Never-before-seen fossils of newly hatched crocodile-like creatures are shining new light on how our aquatic ancestors conquered land.

Early four-limbed vertebrates (tetrapods), which would eventually give rise to humans, took their first steps on land in the Devonian period, some 419 million to 359 million years ago, marking one of the most important periods in the evolutionary history of animals.

Now, a new study published Thursday (June 18) in the journal Science has revealed that these early tetrapods were less like amphibians and more like us. Rather than having a tadpole phase in their development, as many amphibians do today, new evidence suggests that they were direct developers — growing from smaller to bigger versions of themselves, like their ancestors, humans and many other animals.

The study is an important contribution to our understanding of early tetrapods' reproductive developmental biology, said Tim Smithson, a visiting academic at the University of Cambridge who specializes in early tetrapods but was not involved in the study.

It suggests that the "earliest tetrapods that took those first steps on to land were able to rely on the successful reproductive and developmental strategies of their forebears," Smithson told Live Science in an email. "Direct development made life easier — one less thing to worry about!"

The new research was based partly on fossils from early land-dwelling predators called embolomeres. These animals looked like a cross between a crocodile and an eel and ruled river, lake and swamp habitats 350 million to 280 million years ago, during the Carboniferous and Permian periods. While these creatures could grow to more than 10 feet (3 meters) long as adults, the study unveils rare fossils from Mazon Creek, near Chicago, that preserved embolomeres as hatchlings that were days to a couple of weeks old.

"These are intimate details of the first moments of these animals' lives, and we've never seen that before for this entire part of the evolutionary tree," study co-author Jason Pardo, a postdoctoral fellow of evolutionary biology at Vilnius University in Lithuania and a research associate at the Field Museum in Chicago, told Live Science.

These fossils didn't show evidence of external gills and other tadpole-like features that the researchers would have expected from an early land dweller. The researchers then checked other fossils from before and during the "fin-to-limb transition" but found no evidence of an amphibian-like life cycle in those, either.

"For as long as we've understood evolution, we've assumed this story of how we made that transition from water to land," Pardo said. "We in fact have a completely different story."

Science upended?

A statement released by the Field Museum claimed that the study upends scientists' understanding of how animals conquered the land. However, the experts Live Science spoke to disagreed with this assertion.

"The Mazon Creek material is wonderful, the study is interesting and the interpretation of the fossils is sound, but I don't think the results are terribly surprising," Per Ahlberg, a professor of evolutionary organismal biology at Uppsala University in Sweden, told Live Science in an email.

Ahlberg, who was not involved in the new study, specializes in the early evolution of tetrapods. He noted that scientists knew some early tetrapods had a larval stage similar to that of modern salamanders ‪—‬ namely, those belonging to the group Temnospondyli, which he described as the ancestral stock of modern amphibians. However, he contends that this didn't mean scientists assumed every early tetrapod was the same.

"Nobody has been arguing in recent years that ALL early tetrapods had such a larval stage or that this was essential for enabling the transition to land," Ahlberg said. "I mean, I have been working right at the core of this research field for 40 years and I have never given it any thought."

In response, Pardo agreed that specialists in the field recognized that the data didn't support that early tetrapods had an amphibian-like development. However, he argued that even among specialists, assumptions were still made about metamorphosis — a major developmental transition, like a tadpole transforming into a frog — and amphibian-like bodies.

"Onto something big"

Study co-author Arjan Mann, an assistant curator of early tetrapods at the Field Museum, first saw the study's first baby embolomere fossil during a 2016 trip to the Field Museum while working on his doctorate. At the time, the fossil was a mystery.

Mann and Pardo mused over the fossil's identity for years before high-resolution scans with scanning electron microscopy at the Canadian Museum of Nature confirmed that the ancient creature was an embolomere, according to the museum's statement.

"I think Jason and I both knew we were onto something big, since fossils of this kind of animal and from this phase, and developmental state in early tetrapod evolution have never been found or studied before," Mann told Live Science in an email.

Along with the embolomeres, the researchers looked at megalichthyid fish from before the land transition and limbless, snake-like creatures known as aistopods from during the land transition. All showed signs of direct development, they said.

"I think the take home message of this study is that we should always challenge conventional wisdom in science, especially when these older ideas do not have substantial backing," Mann said.

Scientists have discovered a vast whale graveyard stretching for hundreds of miles in the Indian Ocean, with some fossil bones dating back over 5 million years.

The deep-sea "megasite," which the researchers have named the Diamantina Zone necropolis, is the most extensive accumulation of whale carcasses and fossils ever found, the researchers reported in a new study published Wednesday (June 10) in the journal Nature.

"It covers over 1,200 kilometers [750 miles], which just defies belief," Nick Pyenson, a curator of fossil marine mammals at the Smithsonian National Museum of Natural History in Washington, D.C., who wasn't involved in the study, told Live Science. "'Megasite' is a totally appropriate term. I think they've uncovered something really special."

"The density is crazy"

Xiaotong Peng, a deep-sea researcher at the Chinese Academy of Sciences' Institute of Deep-sea Science and Engineering, and his colleagues used an underwater vehicle called the Fendouzhe submersible to survey the seafloor in the Diamantina Zone, an area of ridges and fractures in the southeastern Indian Ocean.

After initially spotting one fossil, the team conducted 32 dives covering a survey area of about 0.25 square miles (0.64 square kilometers). In total, they identified 476 whale fossils and five carcasses of whales that had died more recently, known as whale falls, at depths of between 13,800 and 23,000 feet (4,200 to 7,000 meters).

Extrapolating from these figures, the authors said there could be seven to eight whale carcasses and about 750 fossils per square kilometer in the area.

The largest carcass is a 16.4-foot-long (5 m) skeleton from an Antarctic minke whale (Balaenoptera bonaerensis), the researchers said, but most of the remains are from beaked whales ‪—‬ marine mammals we know little about because they live in the open ocean and spend a lot of time diving.

The five active whale falls are covered in bacteria that live without light or oxygen and break down the oils in the whales' bones, producing hydrogen sulfide. This source of chemical energy enables the carcasses to host diverse communities of jellyfish, brittle stars, bone-eating Osedax worms and bivalve mollusks, which together reach densities of up to 2,840 individuals per square meter, the authors discovered.

Many of the members of the whale-fall communities may also be newly discovered species, the authors wrote, because although most could be matched to the genus or family level using DNA data from samples, only one could be confidently assigned to a species: a clam known as Abyssogena southwardae.

"The density is crazy, as is the fact that they're probably all new to science," said Stephen Godfrey, curator of paleontology at the Calvert Marine Museum in Maryland who wasn't involved in the study. "It's like each one of these whale falls is a new little restaurant that opens up in a 1,200-kilometer-long [745 miles] strip mall," he told Live Science.

These are the deepest whale-fall communities ever found, with the one at about 22,000 feet (6,700 m) being about 8,200 feet (2,500 m) deeper than any other known one, according to the study authors.

A fossil deposit being formed

Peng and his colleagues recovered 43 fossils and dated 33 of them based on the ratios of strontium isotopes present. The fossils belonged to five beaked whale species and one species of baleen whale, a group that includes bowhead and humpback whales.

The oldest fossil found in the area belonged to an extinct beaked whale in the Pterocetus genus that dates back about 5.3 million years, to the Early Pliocene. Another fossil find represented a new species, which the authors have named Pterocetus diamantina.

All that remains of most of the specimens is the bony upper jaw, or rostrum. These fossils came mainly from two species: the Andrews' beaked whale (Mesoplodon bowdoini) and the strap-toothed whale (Mesoplodon layardii). Both of these species still inhabit the Indian Ocean, but the fossils the team discovered could be up to 1 million years old.

"The really awesome thing is that this megasite is showing beaked whale ecology over geologic time scales, so you are getting extinct species overlapping the fossil remains of extant species," Pyenson said.

The megasite is analogous to either the famous Lagerstätte fossil deposits, where there is high-quality preservation, including of soft tissue, or to the Burgess Shale in Canada, which has a huge abundance of animals, Godfrey said, "only here, you have one that's still forming."

Beaked whales are rarely seen, so it might seem strange to find the remains of so many individuals in one place. But Godfrey said these animals might preserve better because of the staying power of their rostra, which have one of the highest known bone densities and mineral contents among living vertebrates.

This means they can persist long enough at great depths without being dissolved or consumed by bone-eating worms that they then become encrusted with ferromanganese oxides, solidifying and encasing the bone in a kind of natural sarcophagus.

"This seals the specimen in, so it will last in perpetuity, or at least over 5 million years, and who knows how much longer," Godfrey said.

Why so many dead whales?

The authors saw many squid and fish in the dives in the Diamantina Zone, which suggests the area provides an ideal deep-water foraging ground for beaked whales. This might mean more whales live and die in the area, even though when a whale dies, its decomposition can make it expand with gas and float on the surface for great distances before eventually falling to the seabed.

Peng and his colleagues also suggested that there might be an increased risk of death by beaked whales being tempted to chase prey below their maximum observed diving depth of about 10,000 feet (3,000 m), which puts them at risk of lung collapse or decompression sickness.

Another possibility is that the V-shaped topography of the Diamantina Zone may funnel sinking carcasses into a smaller area, the authors suggested.

"I think what they're dealing with is an analogue to the terrestrial tar pits or caves that are natural traps where biological remains accumulate over time," Pyenson said.

That's only part of the story, though. Normally, ancient remains on the seabed would get covered by sediment from eroded rocks, so we'd never see the fossils. But the sedimentation rate close to the Diamantina Zone is incredibly low ‪—‬ just 0.02 to 0.22 inches (0.05 to 0.55 centimeters) per 1,000 years, the study authors noted. This means skeletal remains could be exposed for hundreds of thousands of years at the flat bottom parts of the zone and for millions of years on slopes or uplifted sections, the team said.

They think there might be other similar "necropolises" off South Africa, the Iberian Peninsula, and the remote Crozet and Kerguelen islands near Antarctica, where some fossils have already been discovered by trawling.

How much do you know about killer whales? Find out with our orca quiz!

The world's largest known scorpion lived at a time when other land animals were relatively small, around 415 million years ago in what is now the U.K., a new study finds.

The prehistoric creature, named Praearcturus gigas, is estimated to have grown to lengths of around 3.3 feet (1 meter) and was equipped with formidable pincers measuring roughly 6.2 inches (16 centimeters) long, according to a statement from the University of Manchester.

The scorpion would likely have been a fearsome apex predator that stalked floodplains during the Early Devonian Period, when life on land was still in its relatively early stages and dominated by small arthropods. Arthropods are now the most diverse animal group on Earth, as they include insects, crustaceans, scorpions and spiders.

The discovery that such a large scorpion was living 415 million years ago — long before the appearance of complex terrestrial ecosystems, such as forests — offers new insights into the evolutionary history of gigantism in arthropods.

"Confirming that this animal is a scorpion fundamentally changes our understanding of how and when these creatures evolved to such extraordinary sizes," study first author Richard Howard, curator of fossil arthropods at the Natural History Museum, London, said in the statement.

Remains of P. gigas, which have so far been recovered from places in England and Wales, were first documented in the 1870s, but researchers have long debated the type of animal it was.

"Praearcturus has puzzled us palaeontologists for more than a century," study co-author Russell Garwood, a paleontologist at the University of Manchester, said in the statement.

Researchers initially suspected that the remains represented a large woodlouse-like crustacean. Then in the 1980s, research suggested that the fossils instead belonged to a scorpion. But that interpretation was subsequently challenged due to the fragmentary nature of the known remains and a lack of the characteristic scorpion tail.

In the latest study, published Tuesday (June 2) in the journal Palaeontology, the authors re-examined key P. gigas specimens held in the NHM's collections using modern imaging and analytical techniques. They also compared them with other fossil material and recently described prehistoric animals that were more confidently identified as scorpions.

Their analysis indicated that P. gigas is likely a scorpion, and the team also reassigned several other specimens found in the same geological formation to the species, the study reported. Furthermore, the researchers suggested that the creature may have been at least partially aquatic based on the presence of flap-like structures known as epimera — similar to those which provide support and protection to the hard upper shells of lobsters and crabs — in some of the fossils.

"Without complex ecosystems to support Praearcturus on land, these animals probably spent part of their lives hunting in water," Howard said in a Natural History Museum statement.

A semi-aquatic lifestyle could partially explain the scorpion's greater size compared to its modern-day relatives, as water can support large bodies. But it also may reflect the relative lack of competition from other large terrestrial predators, potentially enabling it to reach sizes that would have been more difficult to attain had they been present.

"By bringing together material from several collections and using cutting edge imaging techniques, we've been able to build a clearer picture of the animal than was previously possible, which is really exciting," Garwood said.

"What makes Praearcturus so interesting is that it became enormous at a time when life on land was otherwise very small. But it was a world that could somehow support a giant predator."

A newly discovered feathered dinosaur with four wing-like limbs may have prowled the lakeside forests of what is now northwestern China, gliding between trees like a flying squirrel and snatching some of the earliest birds out of the Cretaceous sky.

The predator, named Jian changmaensis, was a close cousin of Velociraptor and belonged to a strange group of small birdlike dinosaurs called microraptors. Unlike the large and scaly "Jurassic Park" version of raptors, these animals were feathered, lightweight and glided to get around. Based on fossil evidence, J. changmaensis had long feathers on both its arms and legs, giving it the look of a tiny dragon with four wings.

The fossil, described Thursday (June 4) in the journal Annals of Carnegie Museum, is only a partial left shoulder and forelimb. But those bones were enough to reveal a new dinosaur species, and possibly solve a longstanding mystery at China’s Changma Basin, a site packed with ancient bird fossils and broken bird bones that look a lot like the pellets coughed up by modern owls.

"Our team has recovered more than one hundred bird fossils at Changma, but only this single non-avian dinosaur specimen," study co-author Matthew Lamanna, a senior dinosaur researcher and curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh, in a statement.

"[Microraptors] provide a window into what the closest ancestors of the first birds were probably like," he told Live Science via email. "Studying them yields clues as to how birds got their start and how they learned to fly."

Finding a fossil among the fragments

Paleontologists uncovered the fossil in the Lower Cretaceous Xiagou formation near Changma village in the Gansu province. The rocks there were formed during the early Cretaceous period about 124 million to 120 millions ago, when the region held a large lake teeming with birds, fish, turtles and other ancient animals.

The site is famous for fossils of Gansus yumenesis, one of the first Mesozoic birds ever found in China. Since 2002, researchers have recovered more than 100 partial bird skeletons from Changma, including fossils with preserved soft tissue such as feathers, skin and claw sheaths.

"Our subsequent expeditions throughout the rest of the 2000s and into the 2010s established Changma as one of the world's most important fossil bird localities, Lamanna said. "It was an amazing thing to be a part of."

But until now, no one had found a non-avian dinosaur fossil from the basin.

That's what made J. changmaensis stand out. Amidst the fossil fragments, the specimen consisted of a fused shoulder blade, upper arm, radius and ulna. It was preserved in three dimensions, unlike many flattened microraptor fossils from the same area.

"Jian is one of the biggest microraptor specimens that has ever been found," Jingmai O’Connor, the associate curator of fossil reptiles at the Field Museum in Chicago and co-author of the study, said in the statement. "The piece of its upper arm bone that we have is about 4 inches [10 centimeters] long, so the entire dinosaur probably had something like a four-foot [1.2 meter] wingspan, around the size of a barn owl."

Microraptors were not birds. But they were very close relatives of the dinosaur lineage that gave rise to birds. Their bodies have elements that seem to blur the line between bird and dinosaur, including claws, sickle-shaped raptor feet and feathers.

"This is neat, a new fossil of those dinosaurs that were basically on the cusp of becoming true birds," Steve Brusatte, a professor of paleontology and evolution at Scotland’s University of Edinburgh who was not involved in the study, told CNN.

The bird hunter

The Changma Basin may have been a buffet for a tree-climbing predator like J. changmaensis. The site was dominated by early birds, as is evidenced by the many pellet-like remains, possibly the dinner remains of the newfound microraptor species.

Researchers can't prove that Jian made those pellets. But it is the only non-bird body fossil found at Changma so far. Jian was also a carnivore, and was much larger than the birds preserved there.

Other microraptor fossils support the idea that these dinosaurs ate from a wide menu. Previous fossilised specimens have been found with remains of fish, lizards, mammals and birds in their guts, suggesting microraptors were opportunistic hunters rather than picky specialists.

For J. changmaensis, birds may have been especially easy targets. If the dinosaur lived partly in trees and could glide, it may have ambushed early birds from branches or moved through the canopy like a sugar glider, according to the researchers.

"We don’t have very much of Jian, just some bones from the shoulder and forelimb," Lamanna said. "It's enough to know that there was this interesting new microraptor living 120 million years ago in what's now northwestern China, but not enough to be able to learn everything we'd like to learn about these dinosaurs. Maybe one of your readers will eventually become a paleontologist and be the one who finds the rest of Jian."

Around 66 million years ago, a gigantic asteroid smashed into Earth and wreaked chaos globally.

Superheated rock from the impact spewed into the air, creating a mushroom cloud that heated Earth's upper atmosphere to a scorching 439 degrees Fahrenheit (226 degrees Celsius). Mile-high tsunami waves rushed through the Gulf of Mexico and disturbed ocean basins half a world away. Fires raged, burning animals and plants to a crisp. Shock waves propagated, blasting everything in their path. And particles from the collision, including sulfur, shot upward, blocking the sun and falling down as acid rain.

In all, 75% of Earth's species went extinct, including the nonavian dinosaurs. So how did some animals ‪—‬ including species of birds, turtles and mammals ‪—‬ survive the catastrophic asteroid collision and its aftermath?

Size, it turns out, played a crucial role. Earth's largest apex predators and herbivores — dinosaurs like Tyrannosaurus rex and Triceratops, and marine reptiles like plesiosaurs and the behemoth Mosasaurus — were doomed from the moment of impact, Kenneth Lacovara, founding executive director of the Edelman Fossil Park and Museum of Rowan University in New Jersey, told Live Science. That's because their enormity meant they were more likely to be harmed during the initial blast, were unable to hide in a safe place during the apocalyptic aftermath, and needed massive amounts of sustenance to survive in a time when food was scarce.

It's not too surprising that size would be linked to survival, Lacovara said. On land, "it's pretty clear in terms of correlation that you have to be small, and you have to be a burrower to get through this event," said Lacovara, who is also a professor of paleontology and geology at Rowan University. Small animals, such as some lizards and mammals, which were no larger than badgers at that time, were more likely to find shelter from the asteroid's immediate and long-term aftereffects. Other small animals that required less food, such as some turtles and fish, were sheltered in the water.

The avian group that led to modern birds survived likely because they were small and had powerful wings and chest muscles that allowed them to fly well and escape dire situations or find new opportunities. Their chicks also grew quickly, meaning they could soon fend for themselves and not overtax their parents.

This led to an overall shift in the average size of Earth's animals. On land, most of the largest surviving animals were about the size of house cats; in the water, the largest survivors were about the size of a "run-of-the-mill shark," Lacovara said.

What the survivors ate

Diet was likely another important factor, said Roger Benson, a curator of dinosaur paleobiology at the American Museum of Natural History in New York City. The plant eaters and those that ate them were especially hard-hit, as the sun was obstructed for up to a decade. Even with size on their side, some smaller creatures, such as certain lizard and turtle species, went extinct because their diets were too reliant on photosynthesizing plants, Benson said.

Aquatic ecosystems were a bit more shielded from the asteroid's initial impact, especially in deeper oceans and freshwater ecosystems. But as photosynthesizing plankton died off due to a lack of sunlight, food systems collapsed and large marine animals starved. Those that consumed dead, organic detritus had a better chance of survival. Some of those resilient marine creatures included the sea sponges, sharks of the Carcharias genus, and mollusks, including the lineage that led to today's chambered nautilus (Nautilus pompilius).

Seed eaters, including birds, and foraging insectivores, such as the tree-dwelling primate Purgatorius janisae, had a better shot at surviving because their food sources of seeds and insects weren't destroyed by extreme temperature changes and a lack of sunlight.

A common theory is that species with more generalist diets had a better chance of surviving the drastic environmental change. For example, Purgatorius coracis, a small mammal, survived the mass extinction thanks to their wide-ranging diet of insects, fruits and seeds. (This trend holds true for modern animals facing climate change: Those with generalist diets, such as crows and raccoons, are expected to do well because they have a wide range of foods to fall back on in case one food source disappears.)

Some species got lucky if their prey were also survivors. A few aquatic turtle species, like Hutchemys rememdium, had an adaptive feeding habit of eating shelled creatures which were living off detritus in aquatic ecosystems. A 2026 study found this adaptation, called durophagy, was linked to comparatively high survival rates during this mass extinction.

Certain behaviors, such as a higher capacity for reproduction or behavioral flexibility in a changing environment, may have enabled survival Benson said.

Mysterious exceptions

Despite current evidence, there are still unknowns surrounding mass extinction survivorship. Recent research indicates we don't know why certain adaptations helped some species but not others.

For example, many present-day species of bivalves feed on microscopic aquatic organisms that rely on the sun to survive. However, among the aquatic bivalves that survived the asteroid and its impacts, reliance on the sun didn't strongly determine survivorship. In another case, night lizards that survived near the impact site are known to have small litters, which goes against the hypothesis that fecundity is advantageous following extinctions. However, these night lizards' slow metabolisms were likely helpful for their survival, and they persist today, the study noted.

And the discovery that a large, terrestrial croc (Tewkensuchus salamanquensis) survived the asteroid strike in what is now Argentina raises questions about how this 660-pound (300 kilogram) species survived. This also raises questions whether the asteroid's impacts weren't as strong in the Southern Hemisphere as they were in the Northern Hemisphere. For example, the wide diversity of plant fossils uncovered in present-day Argentina suggests plants were able to regrow faster at southernmost latitudes.

"We also don't know why mammals emerged from the extinction as the dominant macrofauna," Lacovara said. One theory is that mammals are more resistant to fungal infections than reptiles are, giving mammals a better shot at surviving the "mini age of fungus" that followed the mass extinction.

After all, how evolution proceeded following the mass extinction is a part of humanity's history. The animals that survived ultimately ushered in the age of mammals, including humans, that continues to this day.

What do you know about crocs? Test your knowledge with our crocodile quiz!

There's a new T. rex in town, but this one didn't hunt on land. It ruled the ancient seas.

Scientists have described a new species of mosasaur, a member of a marine reptile group that lived at the same time as dinosaurs during the Cretaceous period (145 million to 66 million years ago). The newly named species fits into an already known genus: Tylosaurus. But its new species name, Tylosaurus rex — T. rex, for short — sets it apart from the other mosasaur species in the group.

The species name means "king of the tylosaurs," according to a new study published Thursday (May 21) in the journal Bulletin of the American Museum of Natural History. The fossils are about 80 million years old and were discovered mostly in northern Texas decades ago.

The mosasaur T. rex measured up to 43 feet (13 meters) long, or about the length of a tour bus. It had finely serrated teeth, unusually powerful jaws, and evidence on its fossils of violent combat with its own species.

"Everything is bigger in Texas and that includes the mosasaurs, apparently," study first author Amelia Zietlow, a research associate of paleontology at the American Museum of Natural History in New York City, said in a statement.

A misidentified species

While examining a fossil in the American Museum of Natural History's collection, Zietlow noticed that a specimen labeled as Tylosaurus proriger — a well-known mosasaur species first described in 1869 — didn't quite match others of its kind. The unusual fossil was discovered in 1979 near an artificial reservoir outside Dallas.

After comparing the specimen with the original name-bearing fossil of T. proriger held at Harvard's Museum of Comparative Zoology, Zietlow and her colleagues found that it belonged to a newfound species. This specimen wasn't the only misidentified specimen of this species; more than a dozen fossils at other institutions shared the same traits.

Compared with T. proriger, the newly described T. rex was 13 feet (4 m) longer, had finely serrated teeth (which T. proriger lacked) and lived several million years later. Most T. proriger fossils were discovered in what is now Kansas and are roughly 84 million years old, while the fossils now identified as T. rex are mostly from Texas and date to about 80 million years ago. At that time, the Western Interior Seaway stretched from the Gulf of Mexico up to the Arctic and was home to many sea creatures, including mosasaurs.

A violent tyrannical king

The new T. rex's anatomy suggests that, like its mosasaur relatives, it was a formidable marine predator. In addition to its massive size, T. rex had strong jaw and neck muscles.

Some fossils show signs of brutal injuries. One specimen in the collection of the Perot Museum of Nature and Science in Dallas, nicknamed "the Black Knight," is missing the tip of its snout and has a fractured lower jaw. The researchers suspect the damage was caused by another individual of the same species.

"Through our study and examination of well-preserved fossils collected throughout the north Texas region, we have evidence of violence within this species to a degree not previously seen in other Tylosaurus specimens," study co-author Ron Tykoski, vice president of science and curator of vertebrate paleontology at the Perot Museum of Nature and Science, said in the statement.

A name to remember

Other famous mosasaur specimens once identified as T. proriger will now be reassigned to to T. rex, including "Bunker," a large specimen on display at the University of Kansas that was discovered in 1911, and "Sophie," a specimen displayed at the Yale Peabody Museum.

The name also nods to an earlier idea. In the late 1960s, paleontologist John Thurmond recognized that large tylosaurs from northeast Texas might represent an unknown species. He informally called them Tylosaurus thalassotyrannus, meaning "sea tyrant."

This is not the first time "T. rex" has had a naming twist. The land-dwelling Tyrannosaurus rex almost ended up with the name Manospondylus gigas, after paleontologist Edward Cope described two partial backbones from South Dakota in 1892. Those bones were later linked to T. rex, but they were too incomplete to clearly define the species when they were first described. By the time the bones were connected to T. rex, its name was already deeply embedded in scientific literature and popular culture.

While the aquatic T. rex seems to have resolved the misidentification issue, the new study also revisited another long-standing problem in mosasaur research: The dataset used to study mosasaur evolutionary relationships has changed little in nearly 30 years. By reanalyzing the evolutionary data on the species, the team also proposed a new evolutionary family tree among tylosaurs and argued mosasaur evolution needs a broader reassessment.

"This discovery is not just about naming a new species," Zietlow said. "It highlights the need to revisit long-standing assumptions about mosasaur evolution and to modernize the tools we use to study these iconic marine reptiles."

T. rex quiz: How much do you really know about the king of the dinosaurs?

A trove of fossils uncovered in northwestern Canada suggests that complex animals evolved in North America earlier than previously thought.

The site houses more than 100 fossils, including six taxa never found in North America before, with some dating back 567 million years. The findings push back the origins of animals that can move themselves in search of food by several million years, according to a study published May 20 in the journal Science Advances.

"For 3 billion years, life on Earth was dominated by microbes," study co-author Scott D. Evans, assistant curator of invertebrate paleontology at the American Museum of Natural History in New York City, said in a statement. Then, all of a sudden, "we get these strange-looking marine animals big enough to see and capable of behaviors we would find familiar today. If we want to understand this transition, when life first became large, complex and unmistakenly animal, this new site has tremendous potential."

Complex, multicellular animals first evolved during the Ediacaran period (635 million to 541 million years ago). At this time, North America was part of the ancient continent Laurentia, which predated the supercontinent Pangaea.

Some of these early animals from the Ediacaran are linked to modern animals, like mollusks and jellyfish, while others look nothing like any species living today. Most, however, had soft bodies without shells or bones, so fossils from this period are rare.

Scientists split the fossils that did form into three groups, or assemblages, based on when the animals lived. The Avalon assemblage (575 million to 559 million years ago) consisted of stationary animals that lived deep underwater. The White Sea assemblage (559 million to 550 million years ago) contained a more diverse group of animals that lived in shallower water, and the Nama assemblage (550 million to 538 million years ago) included the earliest animals that formed shells and bones.

In the new study, the researchers discovered several fossils of species known to belong to the White Sea assemblage for the first time in North America. These fossils date back 5 million to 10 million years earlier than White Sea assemblage fossils previously found in Europe, Asia and Australia.

Among the fossils were Dickinsonia, a flat, oval-shaped organism that absorbed algae through its entire bottom surface; Funisia, a tube-shaped creature that represents the oldest evidence of sexual reproduction among animals; and Kimberella, an early mollusk that may now be the oldest fossil species to exhibit bilateral symmetry.

"Not only is this new site highly diverse, but also it is from a part of the rock succession where we have previously lacked fossil remains," study co-author Justin Strauss, an Earth scientist at Dartmouth College, said in the statement. "This is really exciting. Given our understanding of the regional geology in northwestern Canada, there is great potential here to revisit our understanding of Ediacaran Earth history."

That potential may apply to the creatures' evolutionary history. Based on the sediment patterns in the surrounding rock, the fossilized organisms found in Canada lived in deeper water than researchers previously thought creatures in the White Sea assemblage lived. That could suggest that the animals first evolved in deep water and gradually expanded their range into shallower water — the opposite of typical animal evolution.

"We think of the deep ocean as a dark, inhospitable place, but it is also relatively stable, with few fluctuations in things like temperature and oxygen essential to most animal life," Evans said in the statement. "This stability may have provided key opportunities to support early animal life."

Gigantic fossils discovered in Thailand reveal the "last titan," a long-necked dinosaur that lived up to 120 million years ago when the region was semi-arid, a new study finds.

Dubbed Nagatitan chaiyaphumensis, the newfound species is the largest sauropod, or long-necked dinosaur, found in Southeast Asia to date. It likely measured about 90 feet (27 meters) in length and weighed around 30 tons (27 metric tons), according to a study published Thursday (May 14) in the journal Scientific Reports.

"Our dinosaur is big by most people's standards — it likely weighed at least 10 tonnes [11 tons] more than Dippy the Diplodocus (Diplodocus carnegii)," study first author Thitiwoot Sethapanichsakul, a paleontologist at University College London, said in a statement. However, it is not the largest known sauropod, weighing less than half as much as its South American relatives Patagotitan and Argentinosaurus.

The research team uncovered the fossils from the Khok Kruat Formation in the Chaiyaphum province of northeastern Thailand. A local resident first spotted the fossils in 2016 in a bone bed on the side of a drying pond.

Among the recovered fossils are several vertebrae, pelvic bones and leg bones, including the dinosaur's right femur, or thigh bone. Though the femur had broken into several pieces, the scientists estimated it would have been about 6.5 feet (2 meters) in length — about as high as a tall human.

N. chaiyaphumensis was a type of dinosaur known as a somphospondylan sauropod, a subgroup of large, long-necked dinosaurs that lived from the late Jurassic through the Cretaceous. Fossils from this group have been found on every continent. The shapes of N. chaiyaphumensis's vertebrae and leg bones set it apart from other previously known sauropods.

The team named the sauropod's genus Nagatitan after Naga, "the mythological serpent-like creature found in various Asian cultures, especially in northeastern Thailand, often associated with water and Buddhism," they wrote in the study. "Titan," meanwhile, is from the giants in Greek mythology. The species name chaiyaphumensis is named for the Chaiyaphum province.

During the Cretaceous (145 million to 66 million years ago), northeastern Thailand would have been a semi-arid environment, and N. chaiyaphumensis would have used its long body and large surface area to shed heat and keep cool. The fossil site was likely part of a river system during that time, so N. chaiyaphumensis would have lived alongside crocodiles, fish and fish-eating pterosaurs.

The fossils were embedded in the youngest rocks in Thailand that still contain dinosaur fossils. Though additional rock layers accumulated atop the N. chaiyaphumensis fossils, the specific conditions later in the Cretaceous period probably prevented the formation of later dinosaur fossils, the researchers said.

"Younger rocks laid down towards the end of the time of the dinosaurs are unlikely to contain dinosaur remains because the region by then had become a shallow sea," Sethapanichsakul said. "So this may be the last or most recent large sauropod we will find in Southeast Asia."

How much do you know about the king of the dinosaurs? Test your knowledge with our T. rex quiz!

Whether it's having the "eye of the tiger" or being lionhearted, references to lions and tigers evoke power and determination. That's not surprising given these animals are both large, powerful felines. But they are distinct species. So what do these iconic cats have in common, and how are they different?

To answer this question, let's consider the two species' appearances, evolutionary histories and how they live their lives as kings of their ecosystems.

Appearance and anatomy

The most obvious difference between modern lions (Panthera leo) and tigers (Panthera tigris) is their distinct physical appearances, particularly their coats.

"Just looking at them, you can clearly tell that tigers have stripes and lions don't," Dell Guglielmo, a zookeeper who cares for lions and tigers at Smithsonian's National Zoo, told Live Science. "The lion males have the large huge mane, and the females do not." In contrast, male and female tigers look the same.

A tiger's stripes help the cat blend in among the patterns of shadows and light created by grasses and trees in the dense temperate and tropical forests of Asia where they live. The orange and brown or black stripes stand out to the human eye, but to a tiger's colorblind prey, orange appears green and blends in. The stripes are pigmented on their skin, too. Each tiger's stripe pattern is unique, Guglielmo said.

Lions' tawny coloring also serves as camouflage. Lions blend in with the dry grasses of Africa's open savannas.

On the inside, however, lions and tigers are very similar. "If you look at the skeletons, all cats essentially look the same," Z. Jack Tseng, an associate professor of integrative biology at the University of California, Berkeley, told Live Science. There's an unofficial saying among those who study cat fossils. If "you ask them to describe the cat family fossil record, usually people will say, 'Well, a cat is a cat is a cat,'" Tseng said. Even your pet cat is basically identical to a lion or tiger, skeletally speaking — just proportionally a lot smaller.

Evolutionary differences

Despite their similarities, "lions and tigers are not each other's closest relatives," Tseng said. Tigers are more closely related to snow leopards, while lions are grouped with leopards and jaguars.

Moreover, tigers emerged much earlier as a species than lions. "The oldest putative tiger fossils are around 2 million years old," Tseng said, "whereas lion fossils are probably no more than a million years old, probably younger than that."

When it comes to classifying cats, size matters. Lions and tigers belong to the Panthera genus, along with leopards, jaguars and snow leopards. The last common ancestor of all five species likely emerged at least 5.57 million years ago, a genetic modeling study found. Tseng and his co-authors modeled this age based on genetic sequences and anatomical data, such as characteristics of bones and teeth. No fossil has been found yet, but this ancestor was likely smaller than lions and tigers, Tseng said.

He noted that both species independently evolved to be large. Animals can grow in body size for a variety of reasons, including living in cooler climates, as this gives them a smaller surface area-to-volume ratio, which helps to reduce heat loss. "The fossil record is not detailed enough to say whether lions and tigers got large independently for the same reasons, but they probably followed one or more of these broader trends as they evolved," Tseng said.

Behavior

Lions and tigers behave quite differently in the wild. Lions live in social, matriarchal groups with multiple female relatives and one or two male adult lions who may leave if challenged by another male. That's where the mane can come in handy.

"Cats often go for the neck when they fight and when they kill their prey," Jacob Shanks, a wildlife care manager at San Diego Zoo Wildlife Alliance, told Live Science. "Male lions being social, there's a lot of battling for territory and access to reproduction and other resources, so the manes help protect against neck wounds."

Tigers have far less social interaction than lions do. Tiger cubs remain with their mother for two years before going their separate ways. As adults, tigers generally avoid each other, aside from breeding. When a tiger wants to approach another individual, it makes a puff-like sound, called a chuff, by pushing air through its nose. Tigers are "one of the only cat species that chuff," Guglielmo said. If the second tiger is OK with the first tiger moving closer, it will chuff back. "Lions don't use a chuff; they just use different body language or just walk up and see if it works," Guglielmo said.

Would tigers and lions ever meet in the wild? That's not likely, as they live in completely different parts of the world. Even in the fossil record, there is no overlap in their range, which prevents the two species from competing and breeding, Tseng said.

However, humans have artificially bred lions and tigers in captivity, creating a hybrid called a liger. "Hybridization doesn't exist in the wild," Shanks said. "I've never seen a case of wild lion-tiger hybridization." Making hybrids doesn't benefit either species, he added.

A key similarity between lions and tigers are the threats they face. Tigers are considered endangered, and lions are vulnerable, according to the International Union for Conservation of Nature. Both big cats face threats from human conflict, habitat loss and climate change. "They need active conservation to protect and to help improve if we're going to not have them slip away," Shanks said.

Think you know about lions and tigers? Test your smarts with our big cat quiz!

Birds have spread their wings the world over, but they first took flight at least 150 million years ago, during the dinosaur age.

In his new book "The Story of Birds: A New History from Their Dinosaur Origins to the Present" (Mariner Books, 2026), Steve Brusatte, who is a paleontologist at the University of Edinburgh in Scotland, takes readers on a wild ride from the oldest known bird, Archaeopteryx from Jurassic Germany, through the eras, explaining how two-legged theropod dinosaurs evolved into the more than 10,000 species of birds alive today.

Around 66 million years ago, some of these small, winged creatures survived the asteroid that killed the nonavian dinosaurs. While many birds stayed small, others grew to huge sizes . Brusatte describes a bevy of lost giants, including colossus penguins, which were gorilla-size apex predators who prowled the oceans, elephant birds that stood as high as a basketball hoop and laid watermelon-size eggs, and terror birds that hammered their prey into submission with razor beaks.

Like Brusatte's other books, "The Rise and Fall of the Dinosaurs: A New History of a Lost World" (William Morrow, 2018) — which landed him the role as scientific advisor on the "Jurassic World" movies — and "The Rise and Reign of the Mammals: A New History, from the Shadow of the Dinosaurs to Us" (Mariner Books, 2022), he starts each new section with a vignette, drawing readers into past worlds. You can read an excerpt on Live Science, detailing the discovery of the first known fossilized dinosaur feathers.

Live Science sat down with Brusatte to discuss the original purpose of feathers, how bird flight was an evolutionary accident, and why the modern era may present the biggest threat to birds since the dino-killing asteroid wiped out their relatives.

Laura Geggel: Alright, this is the big question: Are birds dinosaurs?

Steve Brusatte: Birds are dinosaurs. Birds are dinosaurs in the same way that a T. rex or a Triceratops is a dinosaur. And that is because birds evolved from other dinosaurs. They are part of the family tree. They are just a peculiar group of flying dinosaurs. Just like bats are a strange group of flying mammals.

LG: It's thought that birds evolved from shrinking, two-legged theropod dinosaurs. How did this come about?

SB: Birds did not evolve by, let's say, a T. rex mutating into a chicken one day. That's not how evolution works. And what we see from the fossil record is a whole series of transitional fossils of dinosaurs that lived tens of millions, even hundreds of millions of years ago, evolving one by one. [They evolved] the keystone features of birds: feathers, wings, wishbones, hollow bones and big chest muscles for flying. But these things didn't all just evolve at once. They did not evolve for flying. Almost all of these things evolve for other reasons.

We see things like feathers first turn up in dinosaurs that were too big to fly that lived on the ground. These feathers are much simpler than the feathers of birds today. So, we can actually tell that a lot of the things that birds need to fly, the things that make birds, are things that actually evolved in dinosaurs. They are dinosaur features that were repurposed later on by evolution to make a flying bird.

LG: What do feathers do for an animal? Why do we think dinosaurs had them in the first place?

SB: There is nothing else alive today that has feathers. They are a bird hallmark, a calling card for birds. But what we see from fossils is that the ancestors of birds first evolved feathers. Lots of dinosaurs had feathers, so they're really a dinosaur feature.

And the incredible thing is that we see that a lot of dinosaurs had feathers. It isn't just one or two dinosaurs. And it's not even just the dinosaurs that are most birdlike or were the immediate ancestors of birds. It's many dinosaurs. There are meat-eating dinosaurs with feathers, there's plant-eating dinosaurs with feathers. There's little dinosaurs with feathers. Some of the raptor dinosaurs like Velociraptor [had feathers]. There are big dinosaurs with feathers. There's a tyrannosaur from China, a cousin of T. rex that was like 30 feet [9 meters] long that weighed something like a ton. Its body is covered in feathers.

So, if you map this onto the dinosaur family tree, really the only conclusion you can draw is that feathers were normal for dinosaurs. The common ancestor of dinosaurs would have had some kind of feather. But most of these feathers were very simple — they were not quill pens. They didn't make up wings. There's no way they could be used for flying. They looked a lot more like hair, just individual little strands similar to our hair.

The direct evidence from the fossil record [is] that feathers evolved in a simpler form. They must have been used for something else. We don't know exactly, but the best idea is that they evolved for the same reason that hair evolved in mammals, and that was to help regulate the temperature, to keep the body warm. We wouldn't really know that without the fossils. To me, as a paleontologist, that's the really cool part of the story. This is the evidence from many millions of years ago of how birds evolved.

LG: You've actually studied a number of fossils with feathers.

SB: I write about this in the story, the first time I saw a dinosaur wing. And I know it sounds hyperbolic, but it really was kind of a transcendent experience. And I'll explain why. So I was a college student at the time. I was in undergrad and I was on a trip with my mentor with Paul Sereno who's a very famous dinosaur hunter who's discovered dinosaurs all around the world. He brought me along as a research assistant and we were in China, and my god this was the first time I'd been to China, so far away from home. I grew up in the middle part of America. It was just sensory overload.

We were at the museum in Beijing and from across the room I saw on a limestone slab of rock, a dinosaur beautifully preserved. All the bones were there and it was surrounded by a halo of feathers and the arms were lined with quill pens that looked just like the feathers of modern birds.

Now, I had studied dinosaurs by this point. I was building a career in paleontology. I'd read all about birds and bird evolution. I knew that a lot of dinosaurs had feathers. But until it was in front of my own eyes, and until I saw just how similar those feathers were to the feathers of modern birds, how they formed a wing — but it wasn't a bird, it was a raptor dinosaur. Until that moment, it didn't really hit home.

So, I completely understand how this idea that birds evolved from dinosaurs or birds are dinosaurs, that can be a bit off-putting to people, a bit confusing. It just makes your head spin. But when you see it, you really see it. And since then, I've been very fortunate to go back to China to work with many great Chinese colleagues. To work at some of the museums where farmers from northeastern China bring in the fossils of these feathered covered dinosaurs. These were fossils that were formed about 125 million years ago. Volcanoes buried these entire ecosystems; they locked the soft tissues, the fine details into stone, and now the farmers in Liaoning province in China find these in abundance and bring them to museums.

It's been an incredible thing to play a small role alongside a lot of my good friends in China in studying some of these astounding animals that really capture evolution in action.

LG: The birds' reptile cousins, the pterosaurs, were already flying around when birds emerged. Did birds face much competition from their cousins?

SB: Yeah, it's a great question. A lot of people, rightly so, by the way, think that pterosaurs or pterodactyls, are dinosaurs. I mean, you often see them in dinosaur movies, you see them on the dinosaur posters and the dinosaur toy sets — but they're not actually dinosaurs. They're a separate group of reptiles that flew. They're close cousins to dinosaurs, but they are not dinosaurs, the same way a crocodile isn't a lizard.

Remarkably though, it was the pterodactyls that were the first animals with bones to ever evolve powered flight. And by that, I mean the type of flying where you have wings and you actively move those wings up and down to generate the lift and the thrust that you need for flying.

Plenty of animals can more passively fly and glide — flying squirrels, flying fish. But it's only been the pterodactyls, then later the birds, and then the bats among animals with bones that have evolved powered flight. And the pterodactyls did it by at least about 230 million years ago.

There are fossils of that age of fully formed pterodactyls with big wings, not wings made out of feathers. They did it differently. Their wings were made out of skin. They were attached to a single long finger like an E.T. finger. It was the fourth finger, the ring finger.

Now, Archaeopteryx is still the oldest bird [from] about 150 million years ago. That means that for about 80 million years, give or take, the pterosaurs were there alone in the air. I mean there would have been insects and other things, but among animals with bones, they were the only flyers.

So when birds came on the scene, when dinosaurs started to properly fly they were really interlopers in a pterodactyl world, and they really mounted an insurgency. They didn't just take over the world right away. For a long time, birds and pterodactyls lived together. And in fact, the pterodactyls only died when the rest of the non-bird dinosaurs died when the asteroid hit at the end of the Cretaceous 66 million years ago.

Again, you can do the math. That means that for more than 80 million years, there were birds and pterodactyls living together. Ultimately, really, it was just that asteroid that made the birds victorious. If not for that quirk of prehistory, who knows what the modern world might be like.

LG: There were multiple bird lineages, but only one survived the mass extinction. What set it apart?

SB: The day the asteroid hit, the 6-mile-wide [10 km] rock fell out of the sky and triggered earthquakes and tsunamis and wildfires and blocked out the sun for many years, plunging the Earth into a long nuclear winter. I mean, this was carnage.

And 75% of all species died. Among the species that died, [were] yes, T. rex and Triceratops and the long-neck dinosaurs and the duck bill dinosaurs, but also all of the more primitive birds — the ones that still had teeth, that still had long tails, that still had big claws on their hands, like raptor dinosaurs. A whole bunch of those birds were living on the day the asteroid hit, and they didn't make it through.

The only birds that survived are the modern-style birds, the ones that we know. But these are the birds that have beaks instead of teeth. They're the birds that have big wings and big chest muscles so they can fly really well. They're the birds that grow really fast. We don't really see baby birds very much in nature. They are there. You can hear them sometimes in the nest, squawking for their parents to bring them food, but they stay babies for maybe a few months at most. So birds grow super quickly.

These are all things that probably would have helped them stare down that asteroid because when the asteroid hit, you had to confront that with whatever features you had, with whatever the reality of your anatomy or biology was. There was no time for natural selection to slowly, gradually, change you generation by generation. You had to deal with the fires and the earthquakes and the acid rain and the nuclear winter. It all came at you.

If you were able to grow fast, that would help you. You could get through childhood more quickly. You could turn over the generations more quickly [to reproduce and evolve]. If you could fly, that could help you. If you were small — and these birds were small — you could hide away more easily [from predators and the hazardous, post-asteroid world]. And if you had a beak, you could eat seeds. And we know a lot of these birds could eat seeds. We find the fossil gut contents, the last meal fossilized sometimes.

Eating seeds is actually quite difficult to do. There's not a whole lot of animals that specialize in seeds, but it would have been very important if you could do it when the asteroid hit, because when the sun was blocked for a few years by all the soot from the fires and the dust and the grime from the collision, the Earth really would have gone into a winter that lasted several years. It was dark. It was cold. There was very little if any sunlight for plants to photosynthesize. And so ecosystems collapsed like houses of cards.

If you were a plant eater and you ate parts of a growing plant like leaves or fruits or flowers, you'd be in trouble. I mean, that stuff would soon be gone. But we know from modern disasters, forest fires and volcanic eruptions and so on, that seeds can last in the soil longer than any other part of a plant. That's how forests regenerate after a natural disaster.

If you could eat seeds, that might have been your ticket to survive a little bit longer. You had food that other animals couldn't get.

LG: If you fast forward to today, birds are facing many challenges. Do you want to talk about a few and why their numbers are dropping?

SB: I think birds today are facing their greatest challenge since they stared down the asteroid. There have been a number of birds that have gone extinct within human history. And many of those birds only lived in one place, often on one island. They're quite quirky birds, idiosyncratic birds, things like dodos, but also things like moas in New Zealand or elephant birds in Madagascar or a huge number of birds in Hawaii.

But extinction, I think, is really only part of the story. I mean, extinction is extinction. It's final. If the last member of a species dies, it's done. But you can have a species endure, but in a very wounded state.

That seems to be what's happening to a lot of birds, just since the time that my parents graduated from high school in the early 70s. There's been a loss of billions of birds in the standing population of North America. A lot of these species of birds, whether they're robins, different types of song birds, different types of owls or hawks or eagles … it's not that they've gone extinct, it's just that their populations have crashed. And it really is because of land use, it's because of fertilizer, it's because of pollution, it's because of climate change.

First of all, we just have to admit it's an issue, and then we have to find ways to try to mitigate against this. And I think that's where the fossil record comes in. If we have information from past extinctions or information from past episodes of environmental change, we can better understand which types of birds are more vulnerable when the climate changes or land use changes.

It is awesome to study T. rex, of course, but we do study fossils because we see them as relevant to understanding what's happening in the world today. They're clues from prehistory that give us insight. So that's where we're with birds. It is worrying, but I choose to be optimistic, for two reasons mainly.

First is that — bald eagles [and] California condors being two great examples — when we've realized that certain birds are in dire straits, we have done things to protect them. Bald eagles were super rare when I was growing up in the late 80s and early 90s, but by the end of the 90s, they were very common in northern Illinois, especially along the Illinois River, where I'm from.

Now they have these tourist packages, especially in the winter, where you go and you just watch the eagles. There's so many of them fishing on the river. So, that's a great success story, and that gives me optimism.

The other thing that gives me optimism is [that] birds are survivors. If they got through the asteroid, they're survivors. If they've survived the gauntlet of climate change and volcanic eruptions and drifting continents and rising and falling seas and all the other things that have befallen the Earth over the last 150 million years, then at least some birds, I think, will be able to face whatever humans throw at them.

That's not an excuse for us to be completely disrespectful to the environment, but it does mean that in many ways I'm more hopeful that birds can endure than maybe even our own species. We might think it's the age of mammals. We're a mammal, of course. But at least in that way, we're still in the age of dinosaurs.

Editor's note: This interview has been condensed and edited for clarity.

During the Triassic around 205 million years ago, a newly-identified relative of modern crocodiles stalked its prey, but not in the water, a new study finds.

Like other ancient crocodile cousins, this newly identified species hadn't yet ventured into the water. Instead, it hunted its prey on land, much like a modern fox or jackal, the researchers said.

It would have been a fearsome predator, with its fossil suggesting "specialization for a powerful bite," the researchers wrote in the study.

The specimen was originally discovered decades ago, in 1948 at Ghost Ranch, New Mexico, in a well known dinosaur death bed. At the time, it was tentatively cataloged as a specimen of Hesperosuchus agilis, a small, early relative of crocodiles and alligators. But now, the new study shows that the creature's unusually short snout and thick, reinforced skull set it apart as an entirely new genus and species, though the creature lived — and died — at the same time and place as H. agilis.

"This is the first really strong evidence we have of coexistence between two functionally different-looking crocodylomorphs," study co-author Miranda Margulis-Ohnuma, a paleontologist at Yale University, told Live Science. Crocodylomorphs include modern crocodiles, alligators, caimans and their extinct relatives.

The fossil of the short-snouted creature, newly dubbed Eosphorosuchus lacrimosa, was uncovered in a Late Triassic (237 million to 201 million years ago) formation. The animal's skull, the bones of one of its back legs, one vertebra, and three scales were preserved. The creature would have been about the size of a large dog.

"It was in the basement of the Peabody Museum [at Yale] for, literally, 75 years," Margulis-Ohnuma said. "People would sometimes come visit and look at it, but it had never been identified."

In the new study, published Wednesday (April 15) in the journal Proceedings of the Royal Society B: Biological Sciences, Margulis-Ohnuma and her colleagues categorized the fossil in detail and compared it with a fossil of H. agilis found about 15 feet (5 meters) away. The animals in this section of Ghost Ranch lived at the same time, and they died and were buried in a single event, possibly a flood.

E. lacromisa has a much shorter snout than H. agilis, the team found. It also has a larger, triangular postorbital — a bone in the skull — and matching features on its lower jaw that may have accommodated strong muscles for chomping. Together, those traits suggest the creature had a very powerful bite.

Because E. lacrimosa and H. agilis lived alongside each other, the team suspects they occupied different ecological niches. For example, crocodilians with shorter snouts may have fed on larger, less-agile prey than species with longer snouts did.

"It's really cool that it's not a lineage that's just struggling to take off — at this point, there's already diversity," Margulis-Ohnuma said. "We're really getting a snapshot of the very beginning of functional diversity across crocs."

Scientists don't know much about the early stages of crocodylomorph evolution. There aren't many of these animals preserved in the fossil record, Margulis-Ohnuma said, and many crocodylomorph species from the Triassic are represented by a single fossil specimen.

"For early crocs, we're very data deficient, so every new fossil that comes out is changing the story," Margulis-Ohnuma told Live Science. "If we can continue to describe this material that we have, and ideally find new fossils, it will change the story every single time."

Archaeologists in Israel have unearthed 10 "extremely rare" prehistoric stone hand axes that were crafted to deliberately include geological features, including fossils and geodes, a new study finds.

The hand axes were probably made by Homo erectus between 500,000 and 200,000 years ago, likely because our human ancestors thought these objects were imbued with potency and cosmic significance, the study researchers suggested, although others argue further evidence would benefit the study.

The discovery, reported March 17 in the journal Tel Aviv, is the largest concentration of fossil and geode-bearing stone tools found to date: All previous finds were singular stone tools scattered across continents and time periods.

Local resident and study co-author Muataz Shalata discovered several ordinary hand axes in the Sakhnin Valley, Israel, between 2024 and 2025. Following his discovery, Shalata notified Ran Barkai, a professor of archaeology at Tel-Aviv University.

A dedicated survey in 2025 revealed more than 200 hand axes at Sakhnin Valley, including 10 that include fossils, geodes or other geological features, such as hollows that looked like mini-caves and a concretion forming a round ripple-like feature.

These tools are "unique because until now such items were singularly found, only one extraordinary piece here and there," Barkai, the study's first author, told Live Science in an email."

The discovery contributes to a debate regarding whether early humans recognized or consciously noted geological features and fossils, or whether their occurrence in stone tools was merely accidental. However, the new discovery of multiple tools with these features in the same area suggests it was a deliberate act, the researchers said in the study.

Incorporating these fossil-carrying rocks into tools created "true obstacles towards the stone worker and user," Barkai said, because they made the tools more brittle and difficult to shape. Yet, despite these disadvantages, Homo erectus incorporated these features into their hand axes, which suggests it was done deliberately, he said.

Imbued with potency and cosmological significance

The researchers speculate that early humans were drawn to these unusual features and possibly believed they had metaphysical importance. This, the researchers argue, is a behavioral trait seen across cultures and time and even in other primates, suggesting that curiosity about extraordinary objects is an ancient trait. In this case, the researchers "cautiously suggest" that early humans saw these fossils "as traces of a primordial time and place," and ascribed to them a special potency, they wrote in the study.

Once these rocks were crafted into tools, they were mainly used to butcher large animals, including elephants and their extinct relatives, species that were central to early human survival.

This link between elephants and hand axes is supported by the fact that replicas of stone hand axes were sometimes also made from broken elephant bones, suggesting a deeper relationship between humans, elephants and hand axes, according to the study.

When elephant populations began to decline in the Levant (an area in the Eastern Mediterranean) at this time, it likely created a period of great stress, Barkai said. He stated that previous studies have shown that early humans deliberately placed their hand ax production sites along elephant migration routes close to water sources. The researchers called this the "holy triad of elephants, stone and water," suggesting a deep connection between humans and elephants.

The researchers speculated that early humans saw stone not just as a natural resource to be utilized but also as a way to connect with the cosmos. For example, the study found that Homo erectus deliberately shaped a stone ball from a geode — a painstaking process that would have served no practical purpose, suggesting these early hominins likely saw a value beyond the practical in these features.

"Early humans were more and more desperate for the potency of the cosmos to come to their assistance," Barkai said. "I believe that humans were not just manipulating 'natural resources' by using stone tools, but were doing this while paying respect to these entities … thus the stone tools were always conceived as mediators between humans and the cosmos."

Other researchers note that while the findings are significant, more evidence is needed to further support the symbolic inferences. Sarah Wurz, a professor of archaeology at the University of the Witwatersrand in South Africa who was not involved with the study, told Live Science in an email that "these extraordinary hand axe finds are noteworthy and provide new evidence of the perceptive abilities of past humans." However, she added that "further inferential scaffolding [evidence] would strengthen the interpretation of symbolic behavior."

Barkai plans to conduct more excavations that will provide greater insights into these tools and their uses.

"The artifacts that have been retrieved by now are from the surface only," Barkai said. "We plan to conduct excavations at the site in the future, and will surely run these kinds of analyses on items recovered from pristine archaeological context, as we did in the past with very good results."

A newly discovered trove of fossils in southwestern China is shifting the timeline of when complex animals evolved.

The diversity and complexity of animal life is thought to have increased rapidly beginning around 539 million years ago, in an evolutionary burst known as the Cambrian explosion. But the new fossil site suggests that some of that complexity was already present several million years before the Cambrian explosion, during the end of the Ediacaran period (roughly 635 million to 539 million years ago).

Among the fossil finds were bilateral worm-like animals that may have anchored themselves to the seafloor, early comb jellies, and relatives of starfish and sea cucumbers that likely used tentacles on their heads to catch food. Other fossils bore little resemblance to modern animals or to known Ediacaran or Cambrian species.

"One specimen looks a lot like the sand worm from Dune," study co-author Frankie Dunn, a researcher who studies Ediacaran organisms at the Oxford University Museum of Natural History, said in a statement.

Some simple multicellular creatures, such as sponges, first appeared during the Ediacaran period. But most modern animal phyla showed up during the subsequent 13 million- to 25 million-year-long Cambrian explosion, including chordates, the phylum that includes humans and other vertebrates.

The new fossil discovery suggests that some of that complexity had already arisen by the late Ediacaran. Uncovered as part of the Jiangchuan Biota collection of fossils in southwestern China, the collection contains more than 700 specimens of fossilized animals and algae dating to between 554 million and 539 million years ago. Researchers reported the findings Thursday (April 2) in the journal Science.

"When we first saw these specimens, it was clear that this was something totally unique and unexpected," study co-author Luke Parry, a paleobiologist at the University of Oxford, said in the statement.

The fossils from this site are mostly flat imprints of the organism on the surrounding rock, known as carbonaceous films. Unlike the three-dimensional imprints left by durable body parts, such as bones and shells, carbonaceous films capture some details of the organism's soft tissues, such as its gut and mouthparts.

This less-common method of preservation might help to explain why scientists haven't found evidence of these more complex animals in the Cambrian until now.

"Our results indicate that the apparent absence of these complex animal groups from other Ediacaran sites may reflect differences in preservation rather than true biological absence," study co-author Ross Anderson, a researcher who studies the evolution of complex life at the Oxford University Museum of Natural History, said in the statement. "Carbonaceous compressions like those at Jiangchuan are rare in rocks of this age, meaning that similar communities may simply not have been preserved elsewhere."

The discovery of an enigmatic ape's 18 million year-old fossils in Egypt hints that the ancestors of all living apes, a group that includes humans, may have originated in northeast Africa or Arabia, a new study finds.

Scientists have long assumed that modern apes originated in East Africa, but the newfound fossils, which belong to a new genus and species, suggest they emerged farther north.

"Discovering a fossil ape in this region is both significant and somewhat surprising," study first author Shorouq Al-Ashqar, a paleontologist at Mansoura University in Egypt, told Live Science in an email. "But it also highlights how incomplete our picture has been."

Previous research has established that apes first appeared at least 25 million years ago. They soon flourished, diversifying into dozens of species and spreading across Africa, Europe and Asia.

But relatively few of these ancient apes were on the evolutionary line leading to modern apes ‪—‬ a group that includes humans and other great apes, along with gibbons and siamangs. Moreover, the apes that were on our ancestral line seem to have been confined largely to East Africa. As such, this region has long appeared to be a good place to search for the origins of modern apes.

However, after finding the fossilized remains of an ape that lived in what is now northern Egypt between 17 million and 18 million years ago, Al-Ashqar and her colleagues challenge this idea in a study published March 26 in the journal Science.

The remains, discovered in 2023 and 2024, are very incomplete ‪—‬ just a few fragments of lower jawbone and some worn teeth. But Al-Ashqar and her colleagues established that the remains didn't belong to any known ape species. The researchers have assigned the fossils to a new genus and species named Masripithecus moghraensis; the genus name translates to "Egypt monkey or trickster" in Arabic and Greek, while the species name refers to "Wadi Moghra," where it was found.

The find is important, said Sergio Almécija, a biological anthropologist at the Miquel Crusafont Catalan Institute of Paleontology in Spain who was not involved in the study. "Any new fossil ape discovery is precious because of their scarcity, especially when it comes from a region where their presence has previously gone unnoticed," he told Live Science in an email.

To determine where M. moghraensis fits in the ape evolutionary tree, Al-Ashqar and her colleagues looked at the age and anatomy of a range of ape fossils, as well as evolutionary information in the DNA of living apes.

The analysis placed M. moghraensis on the ancestral line of living apes, just before the split between the great-ape group and the gibbon-siamang, or "lesser ape," group. This implies that M. moghraensis was very closely related to the last common ancestor of all living apes. That, in turn, suggests this common ancestor must have lived in roughly the same place as M. moghraensis.

"The highest odds are [that it lived] in the northern part of the Afro-Arabian landmass," study co-author Erik Seiffert, an evolutionary biologist at the University of Southern California in Los Angeles, told Live Science in an email.

However, not everyone agrees with this interpretation. Almécija describes it as "a bit far-fetched." He would like to see far more complete fossils of M. moghraensis before any attempt to update mainstream scientific ideas about the last common ancestor of living apes.

But Al-Ashqar said the jaw and teeth are among the most useful skeletal parts for working out the evolutionary history of apes. "In mammalian palaeontology, dental anatomy is a cornerstone for interpreting diet and evolutionary history," she said.

Moreover, the idea that modern apes originated in North Africa and Arabia about 17 million years ago fits to some extent with known evidence, according to David Alba, a paleontologist at the Miquel Crusafont Catalan Institute of Paleontology who wasn't involved in the analysis.

For instance, today's nonhuman great apes are found in Africa and Southeast Asia, and fossils show great apes once lived in West Asia, too. Given this information, and the fact that today's lesser apes are found in South and Southeast Asia, "modern hominoids [apes] must have gone through northeastern Afro-Arabia," Alba told Live Science in an email, although this doesn't necessarily mean they originated there.

The exact evolutionary significance of M. moghraensis remains unclear, but its discovery hints that there are more ape fossils yet to be found in and around Egypt. "Further work there could significantly refine our understanding of early ape evolution," Al-Ashqar said.

Human origins quiz: How well do you know the story of humanity?

Around 95 million years ago, a Spinosaurus dinosaur with a tall, blade-like crest on its head and a large sail on its back lived in what is now Niger, a new study finds.

The newfound species, which the researchers have named Spinosaurus mirabilis ("astonishing Spinosaurus" in Latin), lived far inland, in river country — which could be the key to settling a debate about whether this dinosaur and its relatives were swimmers, the team reported Thursday (Feb. 19) in the journal Science.

"There's just no way that you're going to find … essentially an aquatic animal hundreds of miles from the shoreline, buried … right in a river deposit," study first author Paul Sereno, a paleontologist at the University of Chicago who led the team that found the fossil, told Live Science.

Sereno's team made the discovery thanks to a Tuareg guide, a member of a local nomadic population that live in the Sahara Desert, who led them to the remote site on an hours-long trek back in 2019. Upon seeing the fossils, the paleontologists noted a peculiarity: The bones were black, caused by an increased concentration of phosphate in the bone. Sereno said that, in his 25 years of fieldwork, he'd never seen fossils that color in the Sahara Desert.

The crest points to a new species

At first, Sereno and the team couldn't figure out how some of the bones fit together with the rest of the skeleton. "We didn't recognize the crest," Sereno said." It was just so weird [and] asymmetrical."

When a larger team returned to the same site in 2022 and uncovered a skull with a partial crest attached, it all clicked. While running CT scans of the fossil and using computer models, the team found lots of fossilized blood vessels inside, plus a surface texture that suggested a keratin sheath covered the bone in real life, which would have made the crest stand up to 20 inches (0.5 meters) tall.

In the paper describing their findings, the researchers called it the tallest crest known in any meat-eating dinosaur and argued it played a decorative role, possibly allowing the animal to identify potential mates or rivals while wading along riverbanks.

So … was Spinosaurus a swimmer?

In recent years, some researchers have argued that Spinosaurus — a genus that includes S. mirabilis, as well as its relatives, such as S. aegyptiacus — chased prey underwater as a marine hunter. For instance, S. mirabilis has the iconic teeth of a fish hunter, with those on the lower jaw protruding outward and fitting neatly between the sharp teeth on the upper jaw, the team reported.

Yet, based on the fossil's location — buried next to two long-necked sauropods in a river bed, and its body shape — Sereno sees "this dinosaur as a kind of ‘hell heron’ that had no problem wading on its sturdy legs into two meters [6.5 feet] of water but probably spent most of its time stalking shallower traps for the many large fish of the day,” he said in a statement.

The back sail would have added so much weight to Spinosaurus' body that it would have made it difficult to move, Sereno noted. So it's unlikely that any members of the genus swam, he said. "It's sacrificing … aspects of its agility for this, but it's an important feature," Serano told Live Science.

In the paper, the researchers compared S. mirabilis' body shape with other living and extinct predators and placed it between semiaquatic waders like herons and aquatic divers like penguins.

"It shows the process of science evaluating evidence and new evidence appearing," Sereno said.

T. rex quiz: How much do you really know about the king of the dinosaurs?

Fragments of a 2.6 million-year-old fossil jaw discovered in northeastern Ethiopia are transforming the picture of early human evolution in Africa. The jaw, from a bipedal hominin — an extinct relative of humans — shows that its kind journeyed far north, to a region where other hominins were already living.

The ancient jaw belongs to the genus Paranthropus and was found more than 620 miles (1,000 kilometers) farther north than any other fossil of its kind.

"Until now, not a single fossil of Paranthropus had been identified" in the Afar region of Ethiopia, researchers wrote in a study published Wednesday (Jan. 21) in the journal Nature. "Hundreds of fossils representing over a dozen species" of hominins had been found in the Afar, study lead author Zeresenay Alemseged, a paleoanthropologist at the University of Chicago, said in a statement, "so the apparent absence of Paranthropus was conspicuous and puzzling to paleoanthropologists, many of whom had concluded the genus simply never ventured that far north."

The genus Paranthropus contains three species distantly related to humans: P. robustus, P. boisei and P. aethiopicus, collectively known as the "robusts." These species walked upright beginning around 2.7 million years ago, but they are unique in having massive teeth and jaws, which earned one fossil skull the nickname "Nutcracker Man." Paranthropus fossils were previously found in locations from southern Ethiopia to southern Africa and have been dated to between 2.8 million and 1.4 million years ago.

Jaw-dropping find

In January 2019, paleoanthropologists discovered a partial lower jaw, designated MLP-3000, at the site of Mille-Logya in the Afar region of northeast Ethiopia. Dated to about 2.6 million years ago, the jaw came from an older individual whose teeth and bone structure resembled those of members of the Paranthropus genus. While one species — P. aethiopicus — has been found in southern Ethiopia, the new MLP-3000 jaw was discovered much farther north than any previous fossil from this genus.

"The discovery of Paranthropus in the Afar provides critical new information," the researchers wrote, suggesting that "the genus could exploit diverse habitats and regions from north Ethiopia to South Africa as Australopithecus and Homo did." This means that Paranthropus likely had a much more flexible diet than the "Nutcracker Man" moniker suggests, enabling these hominins to disperse and adapt to a wide range of environmental conditions.

The newfound Paranthropus fossil at Mille-Logya adds a third genus to the variety of hominins present in the Afar region between 2.8 million and 2.5 million years ago, including Australopithecus and early Homo. It is not yet clear, though, whether the species would have encountered one another directly.

"Discoveries like this really trigger interesting questions in terms of reviewing, revising, and then coming up with new hypotheses as to what the key differences were between the main hominin groups," Alemseged said.

Carol Ward, a biological anthropologist at the University of Missouri who was not involved in the study, wrote in an accompanying perspective that, given the diversity of hominin species present, "the revelation that Paranthropus inhabited the Afar between 3 million and 2.4 million years ago is particularly exciting."

Although all humans on the planet today are one species, hominin diversity lasted millions of years, until our extinct cousins the Neanderthals and Denisovans disappeared more than 30,000 years ago, Ward noted.

"Researchers can no longer accept that humans evolved from a single lineage of species marching towards modernity in isolation from others," she wrote.

Human origins quiz: How well do you know the story of humanity?

The discovery of a never-before-seen bump on the leg bone of a 7 million-year-old fossil ape shows it walked upright on two legs while it was on the ground, a new study finds.

Only members of the human lineage have this lump, called the femoral tubercle. That makes the species, Sahelanthropus tchadensis, the earliest known hominin, according to the study, published Jan. 2 in the journal Science Advances. (Hominins are the group of species, including humans, that existed after the split from chimpanzees and bonobos. Walking upright on two legs is a defining characteristic of hominins.)

"That [bump] really sold it to us," study lead author Scott A. Williams, an associate professor of paleoanthropology at New York University, told Live Science. "That really convinced me that, OK, we think it's a biped, and therefore, we think it's a member of the hominin lineage."

The reanalysis of S. tchadensis' femur also confirmed two more human-like anatomical features. First, the bone twisted inward, placing the knees closer together than the hips, as in modern humans. Second, there was a distinct lump on the side of the fossil where the largest glute muscle attaches, which isn't found in living nonhuman apes.

S. tchadesis' curved arm bones suggest that, like modern-day chimps and bonobos, the species was adapted to climbing trees. But its hips and knees functioned like those of hominins which suggests the ape frequently walked bipedally while on the ground.

"I think it must have been on the ground a significant amount of the time in order to evolve bipedalism," Williams said.

A hotly debated fossil

Discovered in modern-day Chad, S. tchadensis was first described in 2002 and remains highly controversial. The authors of that study claimed the fossil ape was the earliest known hominin based on the position of the opening in the skull where the spinal cord attaches, called the foramen magnum. The opening was in the middle of the skull, which suggests the ape stood upright like humans do, but others argued that positioning didn't prove S. tchadensis walked on two feet.

Twenty years later, two forearm bones, or ulnae, and a femur fragment belonging to S. tchadensis were revealed. The authors argued that the femur belonged to an ape that walked on two legs. But other scientists disagreed with this assessment, stating that the thigh bone shape did not indicate frequent bipedality.

Williams said he was on the fence about S. tchadensis being bipedal — and, therefore, a hominin — because it is "really old." The ape lived around the time scientists believe the last common ancestor of humans and chimpanzees lived, approximately 6 million to 7 million years ago. Rather than being a hominin, S. tchadensis may have been an ancient ape more closely related to chimps and bonobos than to humans, he explained.

Because he was interested in the answer either way, Williams and his team inspected the 3D scans of limb bones. They looked at various hallmark features on the femur and compared them to the thigh bones of all living and extinct ape species for which these bones exist.

This analysis revealed that the size and shape of S. tchadensis' ulna and femur resembled those of modern-day chimps and bonobos. "We were getting a very great-ape signal," Williams said.

But there were key differences that convinced the team that this ape was bipedal. Their analyses confirmed the presence of an inwardly twisted femur shaft and the attachment for the largest glute muscle, both linked to a hominin way of moving.

Critically, however, they spotted something no one had previously noticed: a tiny bump on the top front of the femur. "It's a very subtle little bump that I actually didn't identify initially by looking at the fossil but by rubbing my thumb along it and bumping into it," Williams said. The team then verified that the original S. tchadensis fossil also had this lump.

"It's beyond convincing," Jeremy DeSilva, a biological anthropologist at Dartmouth College who was not involved in the research, told Live Science. "I immediately pulled this [the femur 3D scan] out and said, 'Wait, how did I not see this?' And sure as day, some of the key anatomies that they point out in this paper, I can see in this fossil," he said. "I'm kind of kicking myself. I wish I had seen these things."

This research makes the question of what the last common ancestor between humans and chimpanzees looked like "even more puzzling and fascinating," DeSilva said.

If S. tchadensis was a hominin, it could suggest, as Williams believes, that this ancestor was more chimpanzee-like than human-like. However, DeSilva said S. tchadensis could potentially be a bipedal ape not on the human lineage.

"So the question we now have as a field that we have to contend with is," he said, "can you be bipedal and not be a hominin? Is that possible?"

Human evolution quiz: What do you know about Homo sapiens?

Around 125 million years ago, a dinosaur longer than a pickup truck stalked rivers to gobble up fish in what is now Thailand.

The remains of the roughly 25-foot-long (7 to 8 meters) dinosaur, which include parts of its spine, pelvis and tail, represent one of the most complete spinosaurid specimens ever found in Asia, according to researchers.

Spinosaurids were a family of bipedal predators with elongated snouts, crocodile-like teeth and, in many species, sails on their backs. Researchers believe that the Thai specimen, first discovered in 2004, belonged to the Spinosaurinae subfamily, which included the longest-known carnivorous dinosaur genus, Spinosaurus — a potential swimming predator from North Africa that grew up to around 50 feet (15 m) long.

"This discovery from Thailand helps us better understand what spinosaurines looked like and how they evolved in Asia," Adun Samathi, an assistant professor at the Walai Rukhavej Botanical Research Institute and Mahasarakham University in Thailand, told Live Science in an email. "[The fossils] also show that dinosaur diversity in Southeast Asia was richer than previously known and expand our understanding of how these unusual fish-eating predators were spread around the world."

Samathi presented the spinosaurid findings Nov. 12 at the Society of Vertebrate Paleontology 2025 annual meeting in Birmingham, England. The findings haven't been peer-reviewed, as Samathi and his colleagues still have to submit them to a journal.

The researchers don't have an official name for the dinosaur. However, they've nicknamed it the Sam Ran spinosaurid, as it was found in the Sam Ran locality (area) of the Khok Kruat rock formation in northeastern Thailand, according to Samathi, who studied the spinosaurid as part of his doctoral thesis. (Samathi is one of several students and researchers to study the specimen since its discovery.)

The team quickly identified the dinosaur as a spinosaurid because it has several of the group's characteristic features, including long neck vertebrae and tall spines on its back vertebrae. However, the species also had features that distinguished it from known spinosaurid species, including shorter spines than Spinosaurus and more paddle-like spines than Ichthyovenator from Loas, which borders Thailand.

The team suspects that the Sam Ran spinosaurid was more closely related to Spinosaurus from North Africa than Ichthyovenator from Laos. However, there's a lot of uncertainty surrounding the evolution of Asian spinosaurids, as well as spinosaurids in general, and the researchers' findings are only preliminary at this stage.

The Sam Ran spinosaurid died beside a shallow river before some of its remains were fossilized. Samathi doesn't think that this spinosaurid could swim, but it seemed to be using the river ecosystem, which was teeming with life when the dinosaur perished relatively early in the Cretaceous period (145 million to 66 million years ago).

"The new spinosaur lived (or at least [was] found) in a river system with gently flowing water and occasional floods, within a dry to semi-arid landscape," Samathi said. "The site has yielded a variety of animals, including freshwater sharks, bony fish, turtles, crocodiles, and dinosaurs such as a sauropod and an iguanodontian."

Scientists have reconstructed the head of an ancient human relative from 1.5 million year-old fossilized bones and teeth. But the face staring back is complicating scientists' understanding of early human evolution and dispersal, according to a new study.

The rebuilt fossil skull, called DAN5, shares traits with Homo erectus, the first early human relatives to have modern body proportions and to disperse from Africa. But the skull also has some features associated with the earlier species Homo habilis. The findings suggest a complex evolutionary path from early human ancestors to H. erectus, researchers reported Dec. 16 in the journal Nature Communications.

DAN5 was discovered in the Gona study region of northern Ethiopia and was first reported in a 2020 study published in the journal Science Advances. The fossils are between 1.5 million and 1.6 million years old and were thought to belong to a small H. erectus female based on the shape and size of the skull.

"We already knew that the DAN5 fossil had a small brain, but this new reconstruction shows that the face is also more primitive than classic African Homo erectus of the same antiquity," study co-author Karen Baab, a paleontologist at Midwestern University in Arizona, said in a statement. This could mean that the population from the Gona region might have "retained the anatomy of the population that originally migrated out of Africa approximately 300,000 years earlier," she said.

To reconstruct DAN5's face, the researchers used micro-computerized tomographic (CT) scans of 10 fossils — five fragments of facial bones and five teeth — to build a 3D model. The process was like "a very complicated 3D puzzle, and one where you do not know the exact outcome in advance," Baab said. "Fortunately, we do know how faces fit together in general, so we were not starting from scratch."

The shape of DAN5's braincase was similar to that of H. erectus. But some of the facial features such as large molars and a flat and narrow nose were more similar to features in the older human ancestor H. habilis.

A similar mix of old and new traits was previously observed in 1.8 million-year-old H. erectus fossils from Dmanisi in the Republic of Georgia, which led some scientists to believe that the species evolved in Eurasia from an earlier Homo population. Older H. erectus fossils dating back 1.8 million years have also been found in Africa. But DAN5 is the first African fossil to have the same mixture of attributes as the Dmanisi hominins, which could support the hypothesis that H. erectus evolved primarily in Africa like other hominins before it. Further complicating the picture, though, is the fact that the DAN5 fossils are younger than those from Dmanisi, suggesting the mixture of old and new traits persisted in Africa for at least 300,000 years.

In future work, the team plans to compare the DAN5 fossils to 1 million-year-old human fossils from Europe, including some that have been identified as H. erectus and as Homo antecessor — a later human relative that lived 1.2 million to 0.8 million years ago — to better understand variability in face shape in the early Homo genus. The team also plans to investigate whether DAN5 might be a product of interbreeding between multiple Homo species.

"We're going to need several more fossils dated between one to two million years ago to sort this out," study co-author Michael Rogers, an anthropologist at Southern Connecticut State University, said in the statement.

Human evolution quiz: What do you know about Homo sapiens?

For a half century, the iconic "Lucy" fossil species, Australopithecus afarensis, has held the title of being the most likely direct ancestor of all humans.

But as the list of ancient human relatives has grown and more fossils have been discovered, Lucy's position has increasingly been called into question. Now, a key paper published last month in the journal Nature could overturn that theory entirely, some scientists say.

They argue that, given the new evidence, an older species, Australopithecus anamensis, was our direct ancestor, not Lucy.

The proposal has revealed intense disagreements in the field. Some say A. anamensis is our direct ancestor, others argue that we don't know which Australopithecus species we descended from, and still others say the new analysis doesn't shake up the human family tree at all.

The new discovery is "not altering our picture of human evolution in any way, in my opinion," Zeray Alemseged, a paleoanthropologist and professor of organismal biology and anatomy at the University of Chicago who was not involved in the new study, told Live Science.

Either way, a resolution might not come until more fossils are found.

An iconic species

Understanding the roots of the debate requires going back a century. In 1925, Raymond Dart announced the discovery of the first known Australopithecus — a skull dubbed the Taung Child unearthed in what is now South Africa that dates to around 2.6 million years ago. For the next 50 years, researchers thought that humans descended directly from the Taung Child's species, Australopithecus africanus.

But Lucy's discovery in 1974 at the Hadar site in Ethiopia rewrote that picture. The 3.2 million-year-old fossil became the oldest known australopithecine specimen at the time.

And researchers found her species, A. afarensis, walked upright on two legs similarly to how humans do today, yet it had a smaller brain — about the size of a modern-day chimp's. This suggested Lucy's kind could represent a "halfway" point in human evolution between the last common ancestor with chimps and us, making her species a good candidate for our direct ancestor among the many known hominins, the lineage that encompasses humans and our closest relatives.

Then, in 1979, her status as our direct ancestor was cemented: an assessment of the evolutionary relationships among hominin fossils uncovered until that point suggested Lucy's species gave rise to the genus Homo. In that family tree, A. africanus was demoted from our ancestor to a more distant cousin.

As more australopithecines have been unearthed, the Australopithecus family tree has become bushier and more tangled, complicating the picture of who we may have descended from. But for many anthropologists Lucy's species still reigns, eventually giving rise to the lineage from which modern humans evolved.

Enigmatic foot may rewrite human evolutionary history

Then the new Nature paper was published. Researchers had unearthed new fossil fragments and tied them to a previously discovered, enigmatic 3.4 million-year-old fossil known as the "Burtele foot".

The new tooth and jaw fragments allowed anthropologists to ascribe the foot, for the first time, to a little described and controversial species — Australopithecus deyiremeda, a tree-climbing ancient human relative that walked upright on two legs and lived alongside Lucy's species 3.5 million to 3.3 million years ago at the Woranso-Mille site in Ethiopia.

For Fred Spoor, a professor of evolutionary anatomy at University College London who was not involved in the recent study of the Burtele foot, the new discovery was the nail in the coffin for the theory Lucy's species was our direct ancestor.

That's because the paper suggested that the species tied to the Burtele foot and the South African A. africanus were more closely related to each other than either was to Lucy's species. By that logic, then, A. africanus may not have descended from Lucy's species, but was rather her cousin.

So, it's possible that both A. deyiremeda and A. africanus descended from the more ancient A. anamensis, who lived in East Africa from around 4.2 million to 3.8 million years ago.

This would also make A. anamensis the direct ancestor to humans, Spoor told Live Science in an email.

For Spoor, this finding would have huge implications. "If this is correct, A. afarensis will lose its iconic status as the ancestor of all later hominins," probably including us, Spoor wrote in an accompanying commentary about the recent research.

A fierce debate

But other anthropologists are hotly divided on the implications of the new paper.

Some Live Science spoke to thought Spoor's conclusions were plausible, while other experts said they were "far-fetched" and "a stretch, to put it mildly."

Because the existing fossil record in East Africa goes much further back in time than the current South African record, many believe the Homo genus arose in East Africa.

Currently the oldest known Homo fossil is a 2.8 million-year-old jawbone from Ethiopia, but models estimate the genus would have actually emerged around 0.5 million to 1.5 million years earlier.

This is older than many of the earliest South African hominin fossils, which were found thousands of miles away. That "would make it unlikely that any of those are the direct ancestor," Carol Ward, the Curators' Distinguished Professor of pathology and anatomical sciences at the University of Missouri, told Live Science.

For many, the most likely candidate for an East African ancestor is still Lucy's species, A. afarensis, which lived in modern-day Ethiopia, Tanzania and Kenya from around 3.9 million to 3 million years ago. This wide geographic distribution and persistence for almost a million years means it had many opportunities to give rise to other species across Africa, Alemseged said.

Scientists in the "Lucy" camp argue that A. afarensis' fully upright mode of walking, broad diet, use of early stone tools and wide geographic range constitute strong evidence for Lucy's ancestral position in the human family tree.

This makes Spoor's claim that Lucy's species wasn't our direct ancestor a big one. But he isn't alone in this view.

Thomas Cody Prang, an assistant professor of biological anthropology at Washington University in St. Louis and a co-author of the Nature study, said it's possible A. afarensis evolved human-like features completely independently of modern humans, like how bats and birds independently evolved wings. Such convergent evolution has been proposed before in our family tree: For example, Prang's team previously found that A. afarensis and modern humans independently evolved certain body proportions.

If this is true, other species living at roughly the same time as Lucy's kind are likely ancestors to later hominins, Prang told Live Science in an email.

Prang, for his part, thinks A. deyiremeda's anatomy makes the species a better candidate for our direct ancestor than Lucy. That's because the species has a combination of ancient and new traits. What's more, a 2015 analysis flagged A. deyiremeda as being more closely related to Homo than Lucy's species.

Others think the Nature paper resurrects A. africanus as a plausible ancestor to Homo.

Lauren Schroeder, a paleoanthropologist at the University of Toronto Mississauga and who was not involved in the new study, said that either way, many different hominin species were evolving and intermingling across Africa during this 3.5 million to 2 million period of time. That means our evolutionary history is more like a braided stream, with species separating and then recombining, and less like a straight evolutionary line.

"Early Homo could have emerged from a broader, pan-African pool of australopith diversity. So yes, Lucy’s species is still a candidate, but no longer the candidate," for a direct human ancestor, Schroeder told Live Science in an email.

Even the authors of the new paper disagree on its implications. While Prang supports the dethroning of Lucy's species as our direct ancestor, the study's lead author Yohannes Haile-Selassie, a paleoanthropologist and director of Arizona State University's Institute of Human Origins, insists that Lucy's species is still the best candidate for the direct ancestor to Homo.

He told Live Science in an email that the more ancient traits found in A. deyiremeda and A. africanus, like having feet adapted for climbing trees, contradict the idea that they are our direct ancestors. On the other hand, Lucy's species had more human-like feet, which Haile-Selassie said makes A. afarensis the "more likely ancestor of those which came later."

Of course, it's possible the smoking gun evidence that settles the debate will never come.

"We will almost certainly never know who our direct ancestor is — and the more we learn about human evolution and how diverse our past was, the more elusive that ancestor becomes," said Ward.

But that doesn't mean we'll ultimately understand less of our evolutionary past, Ward said. "Even though we may never know which one was our ancestor, we can still piece together much of what that ancestor may have been like."

Human evolution quiz: What do you know about Homo sapiens?

More than 5,000 years ago, burrowing bees made their homes inside heaps of rodent bones buried in a cave on Hispaniola, the Caribbean island that comprises the Dominican Republic and Haiti, a new fossil study suggests.

The bees encountered the bones while digging to their preferred depth in the soil. They stopped to build nests inside tooth and vertebra cavities, which turned out to be the perfect size, researchers found. Most of the bones the scientists recovered were from hutias — chunky rodents that look like a cross between squirrels and beavers — but a handful were the remains of an extinct type of sloth.

This is the first time that bee nests have been discovered inside preexisting nooks in fossils and only the second piece of evidence of burrowing bees nesting in a cave. Researchers previously documented examples of bees drilling into old bones to make their nests, but the new find suggests the bees readily settled in existing fossil cavities, according to the study, which was published Wednesday (Dec. 17) in the journal Royal Society Open Science.

"The cells of Osnidum almontei [the name given to the fossilized nests] appear highly opportunistic, filling all bony chambers available in the sediment deposit," the researchers wrote in the study.

The bees found the hutia bones a long time after they were deposited in the cave by Hispaniolan barn owls (Tyto ostologa), the researchers posited. Evidence shows that these owls, which are now extinct, sometimes transported hutias into the cave whole, discarding the bones as they devoured the rodents, and sometimes regurgitated pellets containing the remains of hutias they had eaten while hunting. Barn owl bones found in the cave indicate the species lived there, the researchers noted.

These piles of bones became buried over time as sediments washed into the cave from outside. And several generations of burrowing bees took advantage of this much later, even though these bees typically make their nests in the open, according to the study.

In one tooth cavity, the researchers found six nested bee nests, indicating that successive generations made their homes in the same spot after previous nests had been abandoned.

The bees may have chosen to nest in the cave rather than outside it because the surrounding landscape had little to no earth for burrowing. "The area we were collecting in is karst, so it's made of sharp, edgy limestone, and it's lost all of its natural soils," study co-author Mitchell Riegler, a teaching assistant at the University of Florida, said in a statement.

After one of the scientists' last visits to the cave, plans had been submitted to turn it into a septic storage facility.

"We had to go on a rescue mission and get as many fossils out as possible," study lead author Lazaro Viñola Lopez, a paleobiologist at the Field Museum of Natural History in Chicago, said in the statement.

The plans to build a septic tank eventually fell through, but the scientists removed abundant fossils regardless. These fossils have yet to be analyzed, and the team plans to publish more studies about their finds.

It's a long-held idea that turtles can tuck their heads into their shells when threatened. But is it true? And is this protective trick why turtles the world over have shells today?

The answer is that some types of turtles can, and others can't, experts told Live Science. And even though shells can be protective for some of these reptiles, fossil evidence suggests that shells evolved for entirely different reasons.

Tortoises are one type of turtle that can tuck their heads into their shells. This terrestrial subgroup of turtles emerged 50 million years ago, Tyler Lyson, senior curator of vertebrate paleontology at the Denver Museum of Nature and Science, told Live Science. They typically move slowly, so they rely on their shells to protect them from predators. Most tortoises can draw their heads into their shells, which typically also have a domed shape with more space inside to make that possible.

Several terrestrial turtle species, which split their time between land and water, can do the same.

"Turtles have two ways of tucking the head in," Jason Head, a professor of vertebrate evolution and ecology at the University of Cambridge, told Live Science. "We have what are called the side-neck turtles. They have long necks, and they literally fold the head and neck to the side over one of their arms. And then there are the snake-neck or S-neck turtles, which put a loop into the neck, and can actually pull the neck into the shoulder girdle."

One example is the eastern box turtle (Terrapene carolina carolina), whose bottom shell, known as a plastron, is fitted with a hinge that even allows it to completely close up the shell.

But sea turtles are one group of turtles that cannot pull their heads into their shells. Sea turtles have much sleeker, lighter shells that contain no space for them to tuck their heads inside. "This is to lighten the load," Head said, and it allows sea turtles to swim faster to escape predators.

How turtle shells evolved

So, how did some turtles develop this lifesaving trick? To find out, we need to explore how turtle shells evolved, which takes us back almost 300 million years in the fossil record.

"The turtle shell is a complicated structure. It's made up of over 50 bones," Lyson said. "Bone" is the key word, because fossils reveal that turtle shells are part of their skeletons. And while the modern turtle's shell looks like a solid unit, it's actually made up of two skeletal features that evolved separately.

"The first thing we see in the evolution of the turtle shell is the broadening of the ribs, and we see that in Eunotosaurus africanus," a creature that lived in southern Africa 260 million years ago, before dinosaurs roamed Earth, Lyson told Live Science. Lyson first described Eunotosaurus' contribution to turtle evolution in a 2013 study. Researchers think that these creatures spent time burrowing underground to escape the heat and that the development of wider ribs supported more muscle mass that enabled them to do that.

Then, in Germany, the 2015 discovery of a 240 million-year-old fossil called Pappochelys showed a shell-less animal with wider upper ribs paired with thicker belly ribs — known as "gastralia" — on its underside. By 220 million years ago, an aquatic animal called Odontochelys found in China had developed a fully unified belly plate — the plastron — partly from the expanding gastralia.

"Myself and others think that the evolution of the plastron was a ballast for basically going deeper into the water column," Lyson explained. It's also possible the plastron developed to protect turtles from predators swimming below, he noted.

The first evidence of a fully formed turtle shell comes from 210 million years ago, in the shape of a fossilized creature called Proganochelys, whose thick upper ribs had fused together with dermal bone, forming a closed carapace, attached to a lower plastron. The opening for the turtle's head was formed from shoulder bones that connected the top and bottom of its shell, Lyson explained.

Most evidence suggests that these reptilian creatures, called Pantestudines, ultimately led to modern-day turtles. However, Head noted that similar features — like widened, overlapping ribs — also developed in other animals millions of years ago, including some thought to be more closely related to mammals.

"It's an active area of research, with new discoveries coming all the time," Head said.

The shells of these turtle ancestors developed as a response to varied evolutionary pressures, but today, the turtle's shell is used primarily for self-defense, Lyson noted. "The modern-day function isn't necessarily related to how that feature arose," he said. "It wasn't until you got the full advent of the shell that it was for protection."

The turtle's resilient shell has seen these creatures through almost 300 million years of history, and Lyson thinks it's one reason they've managed to survive three of Earth's five mass extinctions.

"We see the fossil record, and we can see the line in the sand where dinosaurs and lots of other things go extinct," Lyson said. "And we see turtles marching right across that line."

Evolution quiz: Can you naturally select the correct answers?

Anacondas have been giant for millions of years, a new study finds.

The enormous snakes' average body size has remained constant since they first appeared in the fossil record about 12.4 million years ago, during the Middle Miocene (16 million to 11.6 million years ago), researchers revealed in a new study published Monday (Dec. 1) in the Journal of Vertebrate Paleontology.

During the Middle and Upper Miocene (12.4 million to 5.3 million years ago), warm temperatures, expansive wetlands and abundant food enabled many animal species to grow much larger than their modern relatives. But few of these giant animals have survived to the present day.

"Other species like giant crocodiles and giant turtles have gone extinct since the Miocene, probably due to cooling global temperatures and shrinking habitats," study co-author Andrés Alfonso-Rojas, a vertebrate paleontologist at the University of Cambridge, said in a statement. "But the giant anacondas have survived — they are super-resilient."

Anacondas make up a group of constricting snakes that today includes the heaviest snake species in the world. Modern anacondas average 13 to 16 feet (4 to 5 meters) in length, though the largest can reach up to 23 feet (7 m). Scientists weren't sure whether anacondas had been even larger during the Miocene, or whether they had been the same size and retained their massive size into the present day.

To estimate how big ancient anacondas might have been, Alfonso-Rojas and his colleagues measured 183 fossilized anaconda vertebrae from at least 32 individual snakes collected in Venezuela. They also used a technique called ancestral state reconstruction to predict the body lengths of ancient anacondas from characteristics of related snakes.

Based on these calculations, the team found that anacondas averaged about 17 feet (5.2 m) long when they first appeared during the Miocene 12 million years ago — roughly the same length as modern anacondas.

"This is a surprising result because we expected to find the ancient anacondas were seven or eight meters [23 to 26 feet] long," Alfonso-Rojas said in the statement. "But we don't have any evidence of a larger snake from the Miocene when global temperatures were warmer."

It's still unclear why anacondas have not become smaller over time.

Although warm weather and abundant wetlands may have enabled anacondas to reach their giant size early in their evolutionary history, cooler temperatures and shrinking ranges haven't forced the snakes to get smaller to adapt. That could suggest that these weren't the primary factors keeping the snakes large in the intervening millennia, the researchers wrote in the study.

Predator-prey interactions likely didn't play a major role in maintaining the snakes' body size, either, the researchers said. A lack of competition for food could have helped the snakes grow large in the first place. But they didn't get smaller as other predators moved into South America during the Pliocene (5.3 million to 2.6 million years ago) and the Pleistocene (2.6 million to 11,700 years ago), suggesting that food availability isn't a big factor in anacondas' giant size.

Snake quiz: How much do you know about the slithering reptiles?

Ancient footprints have revealed that large, bone-crushing dogs stalked the ashy wastes of North America in the wake of a devastating Yellowstone supereruption 12 million years ago.

Researchers uncovered the footprints above the skeletons of extinct rhinoceroses called Teleoceras in the Ashfall Fossil Beds of northeastern Nebraska. The dog tracks mark the first direct evidence of large carnivores in the beds, which are nicknamed "Rhino Pompeii" because they have preserved so many Teleoceras rhinos that perished in widespread fallout from volcanic activity at Yellowstone.

"The eruption was so massive that ash would have fallen like snow 1,000 miles [1,600 kilometers] from the eruption site in Idaho," Ashley Poust, a curator of vertebrate paleontology at the University of Nebraska State Museum, told Live Science. "This would have darkened the skies, buried plant life and water sources, and been a real hazard to anything with a delicate respiratory system."

Ancient horses, giraffe-like camels, numerous rhinos and various other animals were entombed in glass-like ash at the Nebraska site. However, until the footprint discovery, researchers hadn't found hard evidence of large meat eaters in the beds, which is unusual, given the abundance of preserved prey.

The footprints were up to 3.2 inches (8 centimeters) long and 3 inches (7.5 cm) wide, matching those of the large, extinct canids Aelurodon taxoides and Epicyon saevus, which crushed and ate bones like modern hyenas do. Not only do the footprints confirm the presence of large carnivores in the beds, but their positioning above the rhino layers suggests that the dogs survived the cataclysmic event that wiped out many animals.

"Survival of top predators after ecological collapse is a little unexpected and has a lot to teach us about how life responds and recovers after disasters," Poust said. Big predators sit at the top of the food chain, so they normally starve if it collapses.

Poust presented preliminary findings from his research Nov. 12 at the Society of Vertebrate Paleontology 2025 annual meeting in Birmingham, England. The findings haven't been peer-reviewed yet, as Poust and his colleagues still have to complete their research and submit it to a journal.

The clearest trackways were uncovered in 2014 and 2023, according to the researchers. While the footprints have yet to be formally described in a journal, their existence isn't a secret. Poust said people visiting the Ashfall Fossil Beds State Historical Park can see the footprints, and his team has subjected the tracks to laser scanning within the public's view. Epicyon is also listed on the University of Nebraska State Museum's ashfall animals webpage.

Northeastern Nebraska once had a similar environment to the African plains. Poust noted that the Ashfall Fossil Beds preserved a seasonal lake that hosted aquatic life, like turtles, and attracted all manner of animals.

"Imagine a watering hole similar to those on the savanna today, but with slightly unfamiliar animals," Poust said. "The sandy shoreline would have been shared by flocks of birds and herds of short-legged rhinos, camels, and five species of horses, some with three toes on each foot."

The dog tracks are present in multiple ash layers and point in different directions, which Poust and his colleagues say is an indication that the predators were making extended or repeated visits to the area after it was caked in volcanic fallout.

It's not yet clear how the dogs were surviving at the time, but one possibility is that they fed on buried rhinos and other carcasses in the immediate aftermath of the eruption.

"There is some evidence that they may have scavenged among the animals who didn't survive, using the buried rhinos as a food cache," Poust said. "But since we haven't found the bones of these meat eaters, we aren't sure yet whether this was enough to see them through to better times, or whether they eventually had to depart to seek their fortunes elsewhere in the massive disaster zone that covered much of North America."

Giant North American "hell pigs" may have munched on bones around 30 million years ago, while their smaller counterparts ripped through softer material, like flesh, new research finds.

The "hell pigs," scientifically known as Archaeotherium ("ancient beast" in Greek), were a group of pig-like creatures that could be as tall as humans while standing on four legs and potentially weigh more than 2,000 pounds (1,000 kilograms).

Researchers have known about Archaeotherium since 1850. But now, a new tooth analysis reveals that these beasts' feeding strategies were more varied than previously assumed. By examining tooth wear, researchers saw that larger species were crushing bones or other hard material, while smaller species were likely shearing soft foods, potentially giving them different roles on the ancient North American landscape.

"We can't assume that they were doing the same thing," Brynn Wooten, a doctoral candidate at Vanderbilt University in Tennessee, told Live Science.

Wooten presented preliminary findings from her research Thursday (Nov. 13) at the Society of Vertebrate Paleontology 2025 annual meeting. The findings haven't been peer-reviewed yet, as Wooten and her colleagues still have to complete their research and submit it to a journal.

Whale of a pig

Archaeotherium roamed across North America from about 37 million to 23 million years ago. Despite their vaguely hoggish appearance, Archaeotherium was more closely related to whales and hippos than to pigs. Their heads were around 30% of their total body length (it varied by species), but their small brains meant they weren't the brightest tools in the Paleogenic shed.

"Archaeotherium has a brain-to-body mass ratio similar to that of reptiles, so they were very unintelligent creatures," Wooten said. "Their heads were massive, but they had little tiny brain cases."

Researchers previously suggested that Archaeotherium could have been active predators, scavengers and/or vegetation strippers. Bite marks on the fossils of Poebrotherium — small camel relatives that used to roam North America — indicate that Archaeotherium may have hunted Poebrotherium and stored some of the carcasses for leftovers.

For the new research, Wooten and Larisa DeSantis, an associate professor of biological sciences at Vanderbilt University, examined a variety of Archaeotherium teeth from different states, including Nebraska, South Dakota, Oregon and Colorado. By using dental microwear texture analysis, which involves creating 3D scans of the tooth surface with a powerful microscope, they could compare wear variation between the different Archaeotherium teeth.

On the whole, Archaeotherium was typically similar to peccaries (pig-like animals found in the Americas), which shear their food. However, wear on the larger-bodied Archaeotherium was statistically indistinguishable from that of lions and hyenas and indicative of an animal that crushed its food.

"It's really interesting that the large ones are capable of crunching bones," DeSantis told Live Science. "The small ones are not."

The crushing wear could mean that the larger species engaged in more scavenging behaviors, potentially using their great size to bully other predators off their kills, the researchers suggested. On the other hand, the larger Archaeotherium could have been consuming more hard vegetarian foods, such as tubers or woody browse. The soft veggie option for smaller Archaeotherium may have been leaves and grasses.

So far, the dental analysis reveals only the texture of Archaeotherium food — not which species they ate. Wooten will now explore other research techniques, including calcium isotope analysis, to confirm whether bone was part of Archaeotherium's diet.

Rock hyraxes, known in southern Africa more often as "dassies," are furry, thickset creatures with short legs and no discernible tails. They spend much of their time sunning themselves on rocky outcrops.

Another thing they sometimes do is drag their butts along the ground. Dog owners know that this behavior can be a sign of parasitic infections; in hyraxes the reason seems to be less clear, but this action leaves distinctive traces in sandy areas.

Traces and tracks — ancient, fossilized ones — are what we study at the African Centre for Coastal Palaeoscience through the Cape south coast ichnology project. Over the past few decades, we have found almost 400 vertebrate tracksites on this coast, some as old as 400,000 years, in cemented dunes known as aeolianites from the Pleistocene epoch. This epoch lasted from about 2.58 million years ago to about 11,700 years ago.

We're building up a picture of the environment during that period and how the animals and plants of that time lived.

Among our latest finds are two fossilized traces that appear to have been made by rock hyraxes long ago. One is a track site and the other is a butt-drag impression with what may be a fossilized dropping in it.

The probable track site was brought to our attention from a site near Walker Bay on the Cape south coast by an ardent tracker, Mike Fabricius. It is around 76,000 years old. We found the probable butt-drag impression east of Still Bay on the same coast, and it is most likely around 126,000 years old.

The butt-drag impression is the first fossil of its kind to be described from anywhere in the world. In addition, these are the only possible fossilized hyrax tracks ever to be identified. In the world of paleontology, anything this unusual is important and we feel privileged to be able to interpret them.

Interpreting the drag mark

Dating on our sites has been done through a technique known as optically stimulated luminescence, which works by analyzing when materials like sand were last exposed to light.

The butt-drag impression is 95 cm [37.4 inches] long and 13 cm [5.1 inches] wide. It contains five parallel striations. Its outer margins are slightly raised, and within it there is a 2 cm-high [0.8 inch] raised feature, 10 cm by 9 cm [4 by 3.5 inches]. Clearly something was dragged across the surface when it consisted of loose sand.

We considered possible causes other than hyrax buttocks. These included a leopard or an ancestral human dragging prey, or perhaps an elephant dragging its trunk. Firstly, however, these would be expected to leave tracks, and secondly in such interpretations the raised feature could not be explained.

But if it was a hyrax, it would make sense, because the buttock trace would have come after the tracks and wiped them out. And the raised feature might be a coprolite: a fused fossilized mass of hyrax droppings.

Old dung and urine

Rock hyraxes leave much more than just tracks and butt-drag traces. Because they prefer rocky areas, their tracks are not often found, but they polish rock surfaces to a shiny finish. This is similar to what buffalo on the North American prairie do, creating "buffalo rubbing stones".

Hyraxes also leave deposits of urine and dung. Urea and electrolytes are concentrated in their urine, and they excrete large amounts of calcium carbonate. This becomes cemented and forms extensive whitish deposits on rock surfaces. Due to their communal habits, hyraxes often urinate in the same preferred localities over multiple generations.

Their urine and dung often mix to form a substance known as hyraceum — a rock-like mass that can accumulate into extensive, dark, tarry deposits. Hyraceum has been used as a traditional medication to treat a variety of ailments, including epilepsy, and for gynecological purposes.

Hyraceum may be tens of thousands of years old, and can be regarded as a threatened, non-renewable resource. The middens, being sensitive to environmental changes and containing fossil pollen and other evidence of ancient life, form valuable natural archives for interpreting past climates, vegetation and ecology.

Thinking of hyraceum as a trace fossil, something which apparently has not been done before, can help in the protection of this underappreciated resource.

Although fossilized urine is globally uncommon, there is a word to describe it: "urolite", to distinguish it from "coprolite" (fossilized poop). It seems that hyraxes contribute the lion's share of the world's urolite. At paleontology conferences, students can be seen sporting T-shirts that brazenly state: "coprolite happens". In southern Africa, a more appropriate term might be "urolite happens".

Through appreciating the importance of butt-drag impressions, urolites, coprolites and hyraceum, and learning about the environment of rock hyraxes and other animals during the Pleistocene, we will never view these endearing creatures in the same light again.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Almost four decades ago, researchers discovered a collection of perfectly preserved fossils inside an impact crater in the Canadian High Arctic. Now, those remains have finally yielded their secrets, revealing they belong to an extinct species of hornless rhinoceros that lived 23 million years ago.

Scientists have called the animal Epiatheracerium itjilik, with the species name meaning "frost" or "frosty" in Inuktitut. These creatures were similar in size to modern Indian rhinos (Rhinoceros unicornis), according to a statement from the Canadian Museum of Nature (CMN). The newly identified fossils are the only specimen found to date and show that the animal died of unknown causes as a young adult.

"What's remarkable about the Arctic rhino is that the fossil bones are in excellent condition," Marisa Gilbert, a CMN paleobiologist and co-author of a new analysis of the remains, said in the statement. "They are three-dimensionally preserved and have only been partially replaced by minerals. About 75% of the skeleton was discovered, which is incredibly complete for a fossil."

The bones were preserved inside the 14-mile-wide (23 kilometers) impact crater thanks to it rapidly filling with water. The crater formed from an asteroid or comet around the same time that the Arctic rhino lived, which suggests the rhino died inside the crater before it became a lake.

The climate in this region was far warmer then than it is today, and plant remains show that the Canadian High Arctic — specifically, Devon Island in Nunavut, where the crater is located — hosted a temperate forest, according to the statement.

As the Miocene epoch (23 million to 5.3 million years ago) transitioned into the Pliocene epoch (5.3 million to 2.6 million years ago) and finally gave way to the last ice age, the fossils were broken up by freeze and thaw cycles and gradually pushed to the surface of the crater. Researchers then found the fossils in 1986.

Subsequent field trips to the crater uncovered more bones belonging to the Arctic rhino specimen. These expeditions also unearthed another species that lived 23 million years ago, the walking seal (Puijila darwini), which likely lived alongside Arctic rhinos.

Gilbert and her colleagues described E. itjilik based on the characteristics of its teeth, lower jawbone and cranium compared with other rhino species. The researchers then determined the Arctic rhino's place in the rhinoceros evolutionary tree by analyzing the newfound species' ties to 57 extinct and living rhino groups. They published their results Tuesday (Oct. 28) in the journal Nature Ecology and Evolution.

The findings suggest E. itjilik was most closely related to rhinos that lived in what is now Europe earlier than 23 million years ago. True modern rhinos (Rhinocerotidae) evolved about 40 million years ago in North America and Southeast Asia, and their descendants subsequently spread to every continent except South America and Antarctica.

"Today there are only five species of rhinos in Africa and Asia, but in the past they were found in Europe and North America, with more than 50 species known from the fossil record," study lead author Danielle Fraser, a research scientist and head of paleobiology at CMN, said in the statement.

The newfound Arctic rhino is the most northerly rhinoceros ever discovered. The researchers think the species migrated from Europe via the North Atlantic Land Bridge, an ancient passage over Greenland consisting of exposed continental crust.

The North Atlantic Land Bridge emerged in the latter stages of the Cretaceous period (145 million to 66 million years ago), but when it disappeared is debated. Some studies indicate that the land bridge collapsed 56 million years ago; others suggest the bridge was more or less continuous until about 2.7 million years ago.

The new findings lend support to the latter hypothesis, because Rhinocerotidae arrived in Europe 33.9 million years ago, during an extinction and dispersal event known as the Grande Coupure, or "great cut." The new study suggests that by 23 million years ago, these rhinos had arrived in North America, so the land bridge likely persisted at least until the beginning of the Miocene epoch.

"It's always exciting and informative to describe a new species," Fraser said. "Our reconstructions of rhino evolution show that the North Atlantic played a much more important role in their evolution than previously thought."

A pivotal new dinosaur study is finally settling a fierce, four-decade-long debate: Was the small tyrannosaur Nanotyrannus a distinct species or merely a teenage Tyrannosaurus rex? Now, a remarkably complete fossil reveals that Nanotyrannus was real.

For years, key fossils were thought by many paleontologists to be juvenile examples of Tyrannosaurus rex, which lived between 67 million and 66 million years ago in western North America. Rather than settling all arguments, however, this "nano" discovery opens a new chapter in understanding T. rex biology and further debate.

A key source of the argument has been a small 67 million-year-old tyrannosaur skull found in the Hell Creek Formation of Montana in 1942. It was given its own species name Nanotyrannus lancensis, in 1988, meaning that the species was based on a single skull, and no one knew what the rest of its body looked like.

"This has been one of the most controversial topics in all of dinosaur paleontology," study co-author Lindsay Zanno, a paleontologist at North Carolina State University and North Carolina Museum of Natural Sciences, told Live Science.

Apart from the isolated skull, the best skeleton of one of these small-body tyrannosaurs came from the Hell Creek Formation, which also spans parts of North Dakota, South Dakota and Wyoming. This specimen, known as Jane, was still rapidly growing and aged about 11 when it died, and differed in several ways from the lone skull.

Now, Zanno and study co-author James Napoli, an anatomist at Stony Brook University in New York, have described a complete tyrannosaur skeleton that is part of the "Dueling Dinosaurs" fossils, the 67 million-year-old remains of what seemed to be the most complete, yet small, T. rex on record and a Triceratops, possibly locked in combat when they died.

The case for Nanotyrannus

Zanno and Napoli say this "Dueling Dinosaurs" skeleton of a tyrannosaur, also from the Hell Creek Formation, isn't a T.  rex and instead shares features with the N. lancensis skull. Crucially, their analysis of growth rings in the bones, spinal fusion data and developmental anatomy indicates that the fearsome dinosaur was about 20 years old and almost fully grown when it died, rather than being a juvenile.

"We were able to take a thin section of the limb bones of this animal and determine that it was in fact, nearly a full-grown individual even though it was only half the length and about 1/10th of the mass of a full, grown T. rex," Zanno said.

It would have weighed just 1,500 pounds (700 kilograms), whereas an adult T. rex would have weighed in at more like 14,700 to 18,000 pounds (6,700 to 8,200  kg). It also has larger forelimbs, more teeth, fewer tail vertebrae and distinct skull nerve patterns. The researchers reported the research on Thursday (Oct. 30) in the journal Nature.

The two dinosaurs would have had very different ecologies, Zanno said. T. rex was a bulky predator with a massive skull, powerful bite force and serrated teeth the shape of bananas. Nanotyrannus was small and slender, swifter and more agile, with enlarged hands and claws, which it would have used for prey capture, she said.

Paleontologists respond

The wider research community seems convinced by this new evidence that this small dinosaur and T. rex are different species.

"Fundamentally and on balance, it looks pretty solid," Dave Hone, a paleontologist at Queen Mary University of London, told Live Science. "I and many other people who have said we don't think Nanotyrannus is valid have always said that the main reason for this is we just don't have any apparent adult small skeletons and that's obviously a pretty big deal. And this really, really looks like an adult small skeleton."

Steve Brusatte, a paleontologist at the University of Edinburgh in Scotland, thinks similarly. "For many years in my research on tyrannosaurs, I've considered a set of smaller skeletons found in the same rocks as the famous skeletons of huge T. rexes to be juveniles of T. rex rather than a distinctive smaller species," he told Live Science in an email. "Evidence from this exquisite new specimen shows that I was wrong — at least in part. The case for Nanotyrannus, a species of long-armed tyrannosaur smaller than T. rex, looks strong, and I think proven beyond a reasonable doubt now."

Thomas Carr, a paleontologist at Carthage College in Wisconsin who has previously argued that all the fossils are juvenile T. rex, has also changed his mind on that front. "I think they've shown decisively that the dueler is a small adult tyrannosaur, so I don't have a problem with that at all," he told Live Science.

However, Carr disagrees with the family tree that Zanno and Napoli suggest, which has Nanotyrannus as a more primitive group outside the Tyrannosauridae family. He said the specimen should be considered a sister species of T. rex, and should be renamed as Tyrannosaurus lancensis.

Is Jane a new species?

Other parts of Zanno and Napoli's paper are more controversial. They examined more than 200 other tyrannosaur fossils, and say that the Jane skeleton differs both from T. rex and the dueling N. lancensis. Jane would have been slightly larger than the dueler, and has a unique sinus pattern in the palate and a differently shaped bone behind the eye.

This leads them to suggest that Jane represents a new species, Nanotyrannus lethaeus — named for the River Lethe from Greek mythology — although they haven't yet described it fully.

"They may have been separated in time or they may have been overlapping and that's something we are not sure of yet," Zanno said.

Barring further finds that shed more light on Jane's anatomical features, the distinctions here are sufficient to justify two species, Thomas Holtz, a palaeontologist at the University of Maryland, told Live Science in an email.

But many researchers remain unconvinced regarding Jane being a new species. "This second described species of Nanotyrannus is based on a small skeleton that clearly had not stopped growing, so I think it's frankly very hard to tell if this was a Nanotyrannus or a juvenile T. rex," Brusatte said.

"I have a different way of looking at the evidence and that is that Jane is a juvenile T. rex," said Carr, who has studied Jane extensively.

The new study suggests that more than one tyrannosaur species shared the same western North American ecosystem in the final million years before the asteroid impact some 66 million years ago, Zanno said.

"I certainly don't have any a priori problem that there's more than one species of carnivore out there at the same time," Hone said. "It was very weird that there were no others."

But if most of the smaller tyrannosaurs at Hell Creek are species other than T. rex, as Zanno and Napoli suggest, that means there is a lack of analyzed juvenile skeletons that are definitely of T. rex.

"Tyrannosauruses were running around for several million years," Hone said. "They're massive, we found loads of adults and they don't just pop into existence at 10 meters [33 feet] long and 5 tonnes [5.5 tons]. So, where, where are the juveniles?"

This lack of juvenile specimens also means we have to re-evaluate ideas of how T.  rex grew — the previous idea was that the species changed quite dramatically as it reached maturity. "We have to rethink a lot of what we know about T. rex life history, growth, paleobiology, because Nanotyrannus has been used as data to understand T. rex and its biology for decades," Zanno said.

She, Hone and Carr suggest that models of T. rex growth should be based on the development of one of its closest relatives, a dinosaur called Tarbosaurus bataar from Mongolia, for which many skeletons ranging from baby to adult exist. Tarbosaurus young look like scaled-down adults rather than having bigger skeletal differences.

"The overarching mic drop of this paper is that Nanotyrannus is real, its own distinct tyrannosaur species, and that necessitates a fundamental reassessment of tyrannosaur classification and evolution," Brusatte said.

Researchers have virtually reconstructed a crushed and distorted 1 million-year-old human skull discovered in China. The newly restored cranium may have belonged to a relative of the mysterious Denisovans and provides clues to the rapid evolution of Homo sapiens in Asia.

In a study published Thursday (Sept. 25) in the journal Science, researchers presented their reconstruction of the Yunxian 2 skull, which was excavated in 1990 from an archaeological site in Hubei province in central China.

Although experts thought for decades that the Yunxian skull was from the human ancestor Homo erectus, the new analysis revealed the skull is more closely related to "Dragon Man," an extinct species first described after the discovery of a different skull in northeastern China in 2021, and to Denisovans, a mysterious group of humans that went extinct around 30,000 years ago.

After digitally reconstructing the Yunxian 2 skull using computed tomography (CT) scans, researchers noticed that it showed a distinctive combination of traits, including a large cranial capacity, a long and low frontal skull bone, and a narrow space between the eye sockets. This set of characteristics is found in what the researchers call the Homo longi clade, a lineage or group of individuals and their descendants that have the same ancestor.

"The Homo longi clade, containing the Denisovans, lasted for over a million years," study co-author Chris Stringer, a paleoanthropologist at the Natural History Museum in London, told Live Science in an email. "But so did the Neanderthal and sapiens lineages."

Based on statistical data from 57 fossil skulls, the researchers estimated that the Neanderthal clade diverged from a common human ancestor first, around 1.38 million years ago. Then, the H. longi clade diverged around 1.2 million years ago, followed by H. sapiens around 1.02 million years ago. (The earliest clear fossil evidence of H. sapiens, however, comes from 300,000-year-old bones from Jebel Irhoud in Morocco.) This short timeframe suggests that rapid diversification took place in all three human groups.

But the researchers are unsure what may have caused these ancient human groups to develop such diverse appearances so quickly. "They lived in small, relatively isolated populations and adapted to diverse paleoenvironments," study co-author Xijun Ni, a paleoanthropologist at the Chinese Academy of Sciences, told Live Science in an email.

Pushing back the origin of these ancient human groups, however, means experts can look even earlier in time for factors that may have triggered human evolution.

"For example, there were two severe cold events at about 1.1 million and 900,000 years ago," Stringer said, "and that may have catalysed evolutionary and behavioural changes," including extinctions.

Given the 1 million-year-old date of the Yunxian 2 skull and its blend of ancient and modern physical traits, the researchers concluded in their study that it likely represents an early form of the group that includes the Denisovans.

Human evolution quiz: What do you know about Homo sapiens?

Around 95 million years ago, small crocodile-like creatures with strange, sheathed teeth burrowed along the shores of the Western Interior Seaway in what is now southwest Montana, a new study suggests.

The new research describes the first such creature ever discovered — a teenage croc nicknamed Elton that measured about 2 feet (60 centimeters) long from nose to tail tip. Elton's fossilized remains were discovered in 2021 during an organized dig in the Blackleaf geological formation, which dates to the middle of the Cretaceous period (145 million to 66 million years ago).

"We have found dinosaurs (in the Blackleaf) before, but this was the second known vertebrate animal we'd ever found in this formation," lead author Harrison Allen, a doctoral student in paleontology at Stony Brook University in New York, who found the fossil when he was an undergraduate student at Montana State University, said in statement. "It led me down the rabbit hole into this amazing world of prehistoric, extinct crocs and their evolutionary niches."

The first fossil Allen noticed was Elton's skull, which was just 2 inches (5 cm) long and embedded in rock, according to the statement. Allen showed the miniature skull to David Varricchio, a professor of paleobiology, taphonomy and ichnology at Montana State University, who immediately understood the fossil's significance.

"After the dig, Dr. Varricchio told me why he was so excited the day I found the initial specimen," Allen said. "It has so much visible anatomy to explore, and he could see it was a tiny, tiny croc skull, fully articulated and preserved — it was a special thing."

It turns out, Elton belonged to a now-extinct family of crocodile-like creatures, or crocodyliforms, that researchers previously didn't know existed. This family, called Wannchampsidae, sits within the lineage Neosuchia, which includes all modern crocodilians and their closest extinct relatives. Its members lived in North America during the Cretaceous, and they were much smaller than other neosuchian crocs are; had Elton survived until adulthood, he would have grown to just 3 feet (90 cm) long, according to the statement.

Neosuchians are typically semi-aquatic or marine carnivores with simple, conical teeth — but not Elton. He and fellow members of the newfound species, named Thikarisuchus xenodentes, had an assortment of differently shaped teeth, including sheathed and other specialized fangs, which they used to devour plants and insects, according to the statement.

Elton and his kind also lived on land, and they likely made burrows in the ground, based on how densely packed Elton's bones were when Allen and his colleagues analyzed them, the statement said.

Shortly after finding Elton's skull, Allen returned to collect bagfuls of the surrounding sediment to search it for more clues about the animal. He spent hours sifting through the dirt, extracting fragments of bone and reconstructing the Thikarisuchus skeleton bit by bit. He worked with his classmate Dane Johnson, now a paleontology lab and field specialist at the Museum of the Rockies in Montana — often to the tune of Elton John's 1972 song "Crocodile Rock," which inspired the name Elton.

To get a clear picture of the fossils, Allen then made CT scans, which helped him distinguish between the bones and chunks of rock that were still stuck to Elton's remains. "Harrison worked super hard to digitally reconstruct the animal, and it came out beautifully," Varricchio, who is a co-author of the new study, said in the statement.

A detailed description and pictures of T. xenodentes, as well as a discussion of the newfound species' position in the evolutionary tree, are included in the study, published Sept. 22 in the Journal of Vertebrate Paleontology. Notably, the researchers highlight a family of ancient crocodyliforms called Atopasauridae that was previously found in Eurasia and looks like Elton, with a small body size and similar dental features.

"It suggests that during the same time period, we're seeing convergent evolution between two distantly related groups due to similar environmental conditions, prey availability and who-knows-what that prompted crocs on opposite sides of the planet to develop similar features," Allen said.

Paleontologists have uncovered the oldest and most complete dome-headed dinosaur fossils to date in Mongolia's Gobi Desert.

The fossils, which are between 108 million and 115 million years old, push back the timeline for the emergence of dome-head dinosaurs, or pachycephalosaurs, by about 15 million years. The new fossils could also reveal details about the evolution and development of these dinosaurs' bizarre rounded skulls.

"Pachycephalosaurs are iconic dinosaurs, but they're also rare and mysterious," study co-author Lindsay Zanno, a paleontologist at North Carolina State University, said in a statement. These dinos thrived during the Late Cretaceous period (between 86 million and 66 million years ago).

Some scientists think the thick skulls of pachycephalosaurs helped them attract mates and fend off competition, while others suggest that these weirdos didn't butt heads, but instead kick-boxed like kangaroos. But how their rounded skulls developed is a mystery. Most known pachycephalosaur fossils are incomplete, and scientists haven't found many fossils from early in their development.

Now, in a new study, published Wednesday (Sept. 17) in the journal Nature, a group of paleontologists report a fossil that might hold some answers. In eastern Mongolia, the team found the fossilized remains of a dome-headed dinosaur from the Early Cretaceous period (145 million to 100 million years ago). They named the newly discovered species Zavacephalae rinpoche.

Zavacephalae comes from the Tibetan word "zava," meaning root or origin, and the Latin word "cephal," meaning head. "Rinpoche" is a Tibetan word meaning "precious one," so named because the team found the skull sticking out of a cliff like a polished jewel.

The fossil included about 54% of the dinosaur's bones, including the skull and entire tail, as well as several hand and leg bones and stomach stones that helped Z. rinpoche grind its food. In life, the dinosaur likely measured about 3.3 feet (1 meter) long and weighed about 12.9 pounds (5.85 kilograms).

"We age dinosaurs by looking at growth rings in bones, but most pachycephalosaur skeletons are just isolated, fragmentary skulls," Zanno said. "Z. rinpoche is a spectacular find because it has limbs and a complete skull, allowing us to couple growth stage and dome development for the first time."

Z. rinpoche's dome was fully developed, but growth rings in its lower leg bone suggest that the animal was a juvenile and was still growing when it died. Because pachycephalosaurs probably used their domes to attract mates, this suggests that the dinosaur reached sexual maturity before it was fully grown.

"If you need to headbutt yourself into a relationship, it's a good idea to start rehearsing early," Zanno said.

"This specimen is a once-in-a-lifetime discovery," Zanno added. "Z. rinpoche gives us an unprecedented glimpse into the anatomy and biology of pachycephalosaurs."

A stunning fossil find has revealed two baby pterosaurs that were struck down mid-flight in a "catastrophic" tropical storm 150 million years ago.

Researchers carried out an animal post-mortem (necropsy) on two Jurassic pterosaur skeletons from Germany and concluded that violent winds likely drove the flying reptiles into a lagoon, where they drowned under the stormy waves.

Pterosaurs, informally called "pterodactyls," ruled the skies during the age of dinosaurs. The fossilized skeletons documented in the new study belonged to the first pterosaur species ever discovered, Pterodactylus antiquus, which spawned the pterodactyl nickname.

The newborns are two of the smallest P. antiquus specimens ever discovered, with a wingspan of about 8 inches (20 centimeters) — around the size of a small bat. The researchers' analysis of these fossils, published Sept. 5 in the journal Current Biology, suggests that they were probably two of many baby pterosaurs that died in storm-related mass mortality events in the region. Adult P. antiquus had an estimated wingspan of around 3.5 feet (1.1 meters), meaning it likely had a better shot at resisting the winds that doomed the youngsters.

The baby pterosaurs are nicknamed "Lucky" and "Lucky II," according to a statement released by the researchers. While they may have been unlucky to perish in a storm, scientists were lucky that their dainty and delicate skeletons were discovered.

"Pterosaurs had incredibly lightweight skeletons," study lead author Rab Smyth, who conducted the research as part of his doctoral studies at the University of Leicester in the U.K., said in the statement. "Hollow, thin-walled bones are ideal for flight but terrible for fossilisation. The odds of preserving one are already slim and finding a fossil that tells you how the animal died is even rarer."

Related: 'Ash-winged dawn goddess' is oldest pterosaur ever discovered in North America — and it was small enough to sit 'on your shoulder'

The pterosaurs were preserved in the Upper Jurassic Solnhofen platy limestone rock formation, which is about 153 million to 148 million years old and located in Bavaria, southern Germany. Paleontologists have found hundreds of pterosaurs in this formation, which was once a semi-tropical seascape with coral reefs and small islands, according to the study.

Solnhofen's fossils are often well-preserved young pterosaurs, while larger adults are rarer and typically fragmented. This is unusual, given that larger and more robust bones often have a better chance of sticking around in an environment and becoming fossils.

Study co-author David Unwin, a palaeontologist at the University of Leicester, said that the team was very excited when Smyth came across Lucky in the Bergér Museum in Harthof but thought it was a one-off. Then, a year later, Smyth came across Lucky II — currently on display in the Burgermeister Müller in Solnhofen, but owned by the Bavarian State Collection for Palaeontology and Geology in Munich. The researchers examined the fossil with a fluorescent UV torch and saw Lucky II had suffered a telling fracture on its arm (part of its wing) before death.

"It literally leapt out of the rock at us — and our hearts stopped," Unwin said in the statement. "Neither of us will ever forget that moment."

Both Lucky and Lucky II had humeral fractures consistent with excessive wind force during flight, similar to those experienced by birds and bats during severe storms today. The researchers believe that violent gusts of wind swept the young pterosaurs away from the safety of land and forced them into the lagoon. Storm-fueled currents then quickly forced them down into the depths of the water column and buried their bodies in sediment, according to the study.

By studying the two baby pterosaurs, alongside data collected from more than 40 other Pterodactylus individuals, the team concluded that Solnhofen has so many small pterosaurs because of catastrophic mass mortality events like these storms that larger individuals would have been able to resist.

"For centuries, scientists believed that the Solnhofen lagoon ecosystems were dominated by small pterosaurs," Smyth said. "But we now know this view is deeply biased. Many of these pterosaurs weren't native to the lagoon at all. Most are inexperienced juveniles that were likely living on nearby islands that were unfortunately caught up in powerful storms."

For the first time in tropical latitudes, scientists have sequenced ancient DNA from the only mammoth endemic to North and Central America: the Columbian mammoth. The research revealed unexpected — and as yet unexplained — genetic differences that made these animals distinct from their northern counterparts.

Columbian mammoths (Mammuthus columbi) were approximately 13 feet (4 meters) tall and towered over their woolly mammoth (Mammuthus primigenius) relatives, with whom they co-existed and even interbred. Their fossils have been discovered in Canada, the U.S., Mexico and Central America. But information regarding how they evolved in the Americas remains unclear.

Construction beginning in 2019 of the Felipe Ángeles International Airport in Santa Lucía, Mexico, uncovered a vast wealth of Pleistocene (2.6 million to 11,700 years ago) fossils, including more than 100 Columbian mammoths.

The sheer amount of fossils, said Federico Sánchez-Quinto, a paleogenomicist at the National Autonomous University of Mexico's (UNAM) International Laboratory for Human Genome Research, prompted him to reach out to those involved with the excavation. This is what ultimately led to the team’s DNA work.

When an animal dies, its DNA rapidly degrades, something that is compounded further by heat. In that respect, "DNA is like ice cream," Sánchez-Quinto told Live Science, as it preserves better in the cold. Nonetheless, Ángeles Tavares-Guzmán, co-author and biotechnology engineer, was "hopeful" about their chances, especially as another team recently extracted ancient DNA from a similarly warm climate.

Related: 'Closer than people think': Woolly mammoth 'de-extinction' is nearing reality — and we have no idea what happens next

In total, the scientists sequenced 61 mitochondrial genomes from 83 mammoth molars. Five radiocarbon-dated samples indicate they were between 13,000 to 16,000 years old. The research was published Aug. 28 in the journal Science.

By piecing together ancient DNA, scientists can better trace the path mammoths took across the Americas. But in this case, the sequencing revealed some puzzling findings.

Research from 2021 indicates that a previously unknown lineage of the Eurasian steppe mammoth (Mammuthus trogontherii) mated with woolly mammoths (Mammuthus primigenius) before crossing Beringia — an icy land bridge — into North America 800,000 to 400,000 years ago, which ultimately resulted in the Columbian mammoth species.

One theory is that Columbian mammoths continued to migrate southward until eventually reaching what is now Mexico — a theory that would be substantiated by finding animals with similar DNA in both Mexico and farther north.

But instead, the team uncovered evidence that the Columbian mammoths in Mexico are genetically different from those in the U.S. and Canada. In other words, although the Mexican Columbian mammoths are the same species as U.S. and Canadian Columbian mammoths, their specific genetic make-up is different.

The team also found that the common ancestor of the Mexican Columbian mammoths diverged much earlier than those that migrated to and remained within the U.S. and Canada.

Study co-author Eduardo Arrieta-Donato, a researcher at UNAM's International Laboratory for Human Genome Research, suggested thinking of that common ancestor as the Mexican mammoths' great, great, great grandmother. "[She] was already a hybrid of the steppe mammoths and the woolly mammoths from Beringia," he said. As her descendants bred and migrated southward, they may have been isolated from other North American mammoths, which could explain that genetic uniqueness, Arrieta-Donato added.

That uniqueness suggests that Columbian mammoth evolution "was way more complicated than we thought," Sánchez-Quinto said, "and that Mexico bears important genetic variation that is not present in other places."

Interestingly, other Pleistocene species excavated in Mexico also display divergent genetic lineages compared with their northern relatives. For example, genetic variation has also been seen in Pleistocene black bears (Ursus americanus) and in at least one mastodon — an extinct type of elephant-like mammoth relative. One species with genetic variation separating them from their northern counterparts is surprising; three species showing similar genetic distinctions indicates something extraordinary happened as species migrated southward.

The new research "raises several new and very interesting questions," said Love Dalén, a professor of evolutionary genetics at the Centre for Palaeogenetics at Stockholm University who was not involved in the study.

"I am very impressed that Federico and colleagues have managed to get DNA from such heavily degraded samples!” he told Live Science in an email. "It is a mammoth feat to get DNA from tropical Late Pleistocene samples!"

Tavares-Guzmán, Arrieta-Donato and Sánchez-Quinto noted two significant aspects of their paper. First, that successfully extracting ancient DNA in Mexico challenges the expectation that DNA is less likely to be extracted in warm climates. And second, that their work shows that DNA analysis doesn’t need to be exported to other countries. "Labs in the Global South have all the capacity to carry out these projects," Sánchez-Quinto said. "Sometimes what we are missing is the money."

The new research hints that species from Mexico seem to be unique. Discovering exactly why that is, however, requires obtaining more DNA samples from a wider geographic distribution. "This is more than justification to further screen the biodiversity happening at the tropics through time," Sánchez-Quinto said, "which, ideally, should be carried out by local scientists."

Editor's note: This article was updated at 4:50 a.m. on Sept 11 to correct the dates the mammoths lived from 11,000 to 16,000 years ago to 13,000 to 16,000.

Mammoth quiz: Test your knowledge of the ice age beasts

A fossil ankylosaur discovered in the mountains of Morocco in 2023 was adorned with some of the most frightening armor ever seen.

Researchers suggest that this intimidating array of spikes was sexually selected — like a peacock's tail, it originally evolved to attract mates, rather than to deter predators. By supporting this cumbersome display, the dinosaur, named Spicomellus afer, demonstrated that it was a healthy and worthy partner.

A study analyzing the fossilized remains of the S. afer specimen, which dates to the Middle Jurassic (174.7 to 161.5 million years ago), was published Wednesday (Aug. 27) in the journal Nature.

An earlier rib fragment with fused spikes discovered in 2021, also from Morocco, offered the first evidence of this bizarre species.

"It was so weird that the first thing we did was a CT scan to check that it wasn't fake and that somebody hadn't stuck spines onto the top of the ring," lead author Susannah Maidment, a paleontologist at the Natural History Museum in London, told Live Science. It was in fact real, so she and her team traced the site where it had been found, leading to the 2023 discovery in the Middle Atlas Mountains near Boulemane.

Analysis of the new fossil material confirms that S. afer is the earliest known ankylosaur. The specimen comprises vertebral and rib fragments, parts of the pelvis, and osteoderms — bony deposits in the skin seen in modern reptiles such as crocodiles and alligators.

The fossil assemblage helped the authors to reconstruct how the animal may have looked in life. The low-slung, turtle-shaped animal was approximately 13 feet (4 meters) long, according to Maidment. She noted that the skeleton is not complete and that these measurements are likely inexact.

Long spikes extended from osteoderms on its neck, ringing its head in a fantastical array.

"Ankylosaurs have bony collars around their necks but they're normally a series of flat plates that are fused together and just sit around the neck," Maidment said. "This one had a huge, robust, bony collar the shape of the neck with an enormous pair of meter-long spikes sticking out either side."

The longest of the 10 cervical spikes, extending from either side of the neck, reached at least 34 inches (87 centimeters). Additional spikes stuck out from each rib and were actually part of the skeleton.

"When we see features among living animals that are very hypertrophied and seem to have no function — and would be annoying to carry around — they are related to sex in some way or another," Maidment said.

Still, the researchers suggest that these spikes may have served a secondary, defensive purpose.

They speculate that the end of the tail featured a mace-like array. One of the blade-like spines discovered by the researchers was 17 inches (42 cm) long, and was unlikely to have been attached to any other part of the body.

The tail vertebrae that supported this fearsome armature indicate that the mechanisms for the defensive clubs of Cretaceous ankylosaurs were well underway early in the evolution of this group of dinosaurs. "Handle vertebrae" (closely linked bones with no cartilage between them) helped to stabilize the bony appendages for which later ankylosaurs are known.

The fact that S. afer featured similar bones indicates that its armor was not purely decorative — its tail deterred predators too.

Among ankylosaurs, function may have actually followed fashion. The ankylosaurs of the Cretaceous featured much simpler armor that was almost certainly a defense against a growing range of theropod dinosaurs, crocodilians, snakes and mammals that would have seen them as appealing prey.

All humans today are members of the modern human species Homo sapiens — Latin for "knowing man." But we're far from the only humans who ever existed. Fossils are revealing more and more about early humans in the genus Homo — ancestors like Homo erectus (Latin for "upright man"), who lived in Africa, Asia and parts of Europe between 1.9 million and 110,000 years ago.

Scientists now recognize more than a dozen species in the Homo genus. So what, exactly, was the first human species? The answer, it turns out, is not crystal clear.

Fossil finds in Morocco have revealed that anatomically modern humans emerged at least 300,000 years ago. But the oldest human species scientists definitively know about is called Homo habilis, or "handy man" — a tool-using primate who walked upright and lived in Africa between 2.4 million and 1.4 million years ago.

However, earlier fossils hint that other Homo species may predate H. habilis. The scarcity of early human fossils makes it challenging to know if unusual specimens are a newfound species or simply an atypical member of a known species. On top of that, evolution can be gradual, so it's hard to pinpoint when a new species emerges, especially when fossils have a mix of features from different species.

"The process of evolution is continuous, but the labels we place on it for convenience are static," Tim D. White, a paleoanthropologist at the University of California Berkeley, told Live Science.

Related: Why did Homo sapiens outlast all other human species?

Earliest Homo

Most evolutionary theories suggest that H. habilis evolved from an earlier genus of primate named Australopithecus — Latin for "southern ape" because its fossils were first discovered in South Africa.

Various species of Australopithecus lived from about 4.4 million to 1.4 million years ago. It may be that H. habilis evolved directly from the species Australopithecus afarensis — the best-known example of which is "Lucy," who was unearthed at Hadar in Ethiopia in 1974.

The fossils of our genus are usually distinguished from Australopithecus fossils by Homo's distinctively smaller teeth and a relatively large brain, which led to the greater use of stone tools.

But White noted that traits like smaller teeth and bigger brains must have emerged at times in the Australopithecus populations that early Homo evolved from.

"If you had an Australopithecus female, there wasn't a birth at which point she would have christened the child Homo," he said.

As a result, there is no fixed point in time in which Homo originated; instead, the Homo genus emerged roughly between 2 million and 3 million years ago, White said.

Evolving in Africa

Since the 1970s, researchers in Africa have discovered fossils that they've attributed to another ancient species, Homo rudolfensis, which challenges the idea that H. habilis was the earliest Homo.

H. rudolfensis seems to have been physically much bigger, had a larger brain and a flatter facial structure than H. habilis, which may have made it look more like a modern human.

Its fossils are roughly the same age as H. habilis — as much as 2.4 million years old. But "there is only one really good fossil of this Homo rudolfensis," according to the Smithsonian National Museum of Natural History, so scientists don't know if H. rudolfensis is an unusual H. habilis or even an Austrolopithicus with a larger-than-usual brain.

Paleoanthropologist Rick Potts, who heads the Smithsonian Institute's Human Origins program, told Live Science that even older fossils from Africa appear to be from the genus Homo and may predate both of those species.

The oldest of those fossils date from about 2.8 million years ago, but they are only fragments — a few jaw bones and a few teeth — so they are not enough to establish if they came from a different, unnamed species of Homo, he said. A 2025 study found additional teeth dating to 2.59 million and 2.78 million years old that may also belong to this mysterious early Homo species.

So it may be that the first human species has not yet been found. "There's a whole lot of excitement, but there is also a lot of uncertainty, about trying to discover more about the origins of the genus Homo," Potts said.

Human evolution quiz: What do you know about Homo sapiens?

Scientists have discovered a "deceptively cute" ancient whale with large eyes and razor-sharp teeth that devoured prey off Australia around 26 million years ago.

The newly discovered Janjucetus dullardi is one of the earliest known cousins of filter-feeding baleen whales, including the gigantic blue whale (Balaenoptera musculus). However, J. dullardi was much smaller than its living relatives, with a compact body built for speed.

Researchers identified this new species from pieces of skull found on the coast of southeastern Australia. The individual it belonged to was a juvenile or subadult, around 7 feet (2.1 meters) long, according to a study published Tuesday (Aug. 12) in the journal Zoological Journal of the Linnean Society.

"It's essentially a little whale with big eyes and a mouth full of sharp, slicing teeth," study lead author Ruairidh Duncan, a paleontology doctoral student at the Museums Victoria Research Institute and Monash University in Australia, said in a statement. "Imagine the shark-like version of a baleen whale — small and deceptively cute, but definitely not harmless."

Related: Ancient whale 'graveyard' discovered under melting Russian glacier

J. dullardi belonged to a family of small whales called mammalodontids, which lived in warm, shallow waters off Australia and New Zealand during the Oligocene Epoch (33.9 million to 23 million years ago). This is not long, in evolutionary time, from when the ancient ancestors of today’s whales first returned to the ocean some 50 million years ago.

A school principal named Ross Dullard first spotted the J. dullardi fossils while walking along the beach of Half Moon Bay, near Melbourne, in 2019. The fossils were exposed at the base of a wave-eroded rock outcrop — part of a geological formation known as the Jan Juc Marl, which is between about 24 million and 28 million years old. After discovering the fossils, Dullard donated them to Museums Victoria.

"This kind of public discovery and its reporting to the museum is vital," senior study author Erich Fitzgerald, a senior curator of vertebrate paleontology at the Museums Victoria Research Institute, said in the statement. "Ross' discovery has unlocked an entire chapter of whale evolution we've never seen before. It's a reminder that world-changing fossils can be found in your own backyard."

Researchers used photography, microCT scans and other techniques to perform a detailed analysis of the fossils, which included preserved teeth and inner ear structures. The team deduced that J. dullardi was a previously unknown species of mammalodontid and named it after Dullard. One of the reasons researchers could tell it was a young whale was because of a lack of wear on the teeth.

Southeastern Australia has become a hotspot for ancient whale fossils, with two other mammalodontid species recovered from the Jan Juc Marl formation. Researchers continue to find fossils in this region and expect more discoveries in the years ahead, according to the statement.

"This region was once a cradle for some of the most unusual whales in history, and we're only just beginning to uncover their stories," Fitzgerald said.

Floodwater in Texas has uncovered 15 dinosaur footprints dating to 115 million years ago, researchers say.

The prints were discovered in northwest Travis County by volunteers who were helping to clear up debris from the devastating floods that hit the region in July, Travis County judge Andy Brown, the county’s chief executive, told ABC News. The three-clawed prints — each measuring roughly 18 to 20 inches (46 to 51 centimeters) in length — were then confirmed by paleontologist Matthew Brown on Aug. 5.

"The tracks that are unambiguously dinosaurs were left by meat-eating dinosaurs similar to Acrocanthosaurus, a roughly 35-foot-long (11-meter) bipedal carnivore," Brown, who is the director of vertebrate paleontology at the University of Texas at Austin, told CNN.

Acrocanthosaurus lived during the early Cretaceous period, between 115 million and 105 million years ago and is thought to have been the largest predator in what is now North America at the time, according to the North Carolina Museum of Natural Sciences. These carnivorous dinosaurs looked similar to the later Tyrannosaurus rex and reached similar lengths, although T. rex was significantly taller and heavier.

The tracks are laid out in a criss-cross pattern and may have been made by multiple dinosaurs moving together as a group.

"We aim to return to these sites and document tracks both new and old," Brown told Live Science in an email. "There are new and more precise technologies available to us now than existed in the early 1990s when these sites were last studied, and we can potentially use drones and surface scans to make 3D models of the trackways to better understand them."

Related: A brief history of dinosaurs

Brown hopes that this additional data might tell us more about the dinosaurs' behavior, anatomy and how they moved.

Waterways like Sandy Creek, where the prints were discovered, cut through a layer of rock called the Glen Rose Formation, which is roughly 110 million years old. "That's how we know how old the dinosaur tracks are," Brown said. "It's because they're preserved in rock layers that are that old."

Travis County lies roughly 200 miles (320 kilometers) south of Dinosaur Valley State Park, which is known for its well-preserved dinosaur footprints. Brown said it was fairly common to find dinosaur tracks in central Texas.

"Fossilized dinosaur footprints are relatively common in Travis County, in fact researchers from the University of Texas have documented tracks in this area of Sandy Creek in the past, in addition to the discovery of new tracks along the banks of the creek exposed during this historic storm," he said.

Dinosaurs roamed throughout what is now Texas during the Mesozoic Era (252 million to 66 million years ago), but the majority of footprints and fossils unearthed in the state come from the Cretaceous period (144 to 66 million years ago), when the state was covered in soft mud and a shallow sea, according to Dinosaur Valley State Park.

A "most remarkable" monster's fossilized remains from Jurassic Germany is a never-before-seen species, a new study reports.

The marine reptile, which swam in prehistoric oceans about 183 million years ago, has been given the name Plesionectes longicollum, which translates to "long-necked near-swimmer."

P. longicollum is a type of plesiosauroid, an extinct group of long-necked, carnivorous marine reptiles that swam in Earth's oceans during the time when dinosaurs dominated terrestrial environments. This specimen lived during the early Toarcian age (183 million to 174 million years ago) during the Early Jurassic.

The fossilized specimen is about 10 feet (3 meters) long, similar to the length of an alligator, with its neck accounting for slightly less than half of its total span.

The nearly-complete skeleton of the animal contained remnants of fossilized soft tissue and bone, which enabled scientists to determine that P. longicollum is indeed a newly-discovered species — a conclusion past studies were hesitant to make.

The reptile's bones were originally excavated in 1978 from a quarry in Germany, part of the Posidonia Shale formation, which is known for its "exquisitely preserved fossils," according to the study. "This specimen has been in collections for decades, but previous studies never fully explored its distinctive anatomy," study lead author Sven Sachs, a vertebrate paleontologist at the Natural History Museum of Bielefeld in Germany, said in a statement from the museum.

Related: Oldest tadpole on record was a Jurassic giant

The findings were published in the journal PeerJ on Aug. 4.

"Our detailed examination revealed an unusual combination of skeletal features that clearly distinguish it from all previously known plesiosaurs," Sachs said. The work demonstrated that the Posidonia Shale beds contained a higher degree of reptile diversity than previously thought.

The new specimen is the oldest known plesiosaur from the town Holzmaden in southwest Germany, according to the statement. The animal was not yet an adult when it died, but based on its anatomy, researchers were able to classify it into a new genus and species.

Five other almost complete Plesionectes skeletons have been identified at the Posidonia Shale and include examples of all three major plesiosaur lineages.

"This discovery adds another piece to the puzzle of marine ecosystem evolution during a critical time in Earth's history," study co-author Daniel Madzia, a paleobiologist at the Polish Academy of Sciences, said in the statement. The period when P. longicollum lived "was marked by significant environmental changes, including a major oceanic anoxic event that affected marine life worldwide," he said. The event, which depleted oxygen and spiked acidification in the water, led to a severe loss of marine biodiversity, including an extinction event killing around 5% of global families on land and in the sea.

This fossil is permanently housed at the Stuttgart State Museum of Natural History in Germany.

Researchers have discovered the remains of an ancient shark deep inside the world's longest cave system.

The newly discovered shark, plucked from the walls of Mammoth Cave in Kentucky, lived around 340 million years ago and was equipped with a curved row of teeth that it used for crushing its prey.

Macadens olsoni was a small shark, less than 1 foot (30 centimeters) long, and likely fed on mollusks and worms, according to a statement released by the National Park Service (NPS).

"This discovery is a remarkable addition to our understanding of ancient marine life and underscores the importance of preserving and studying our natural history," Barclay Trimble, the superintendent at Mammoth Cave National Park, said in the statement.

Related: 340 million-year-old 'nail tooth' shark found deep inside Mammoth Cave in Kentucky

The rocks of Mammoth Cave formed around 320 to 360 million years ago and were once beneath a shallow saltwater sea, called the Mississippian Sea. The cave system itself is much younger, and only formed about 10 to 15 million years ago, when water from rivers and streams on the surface sank into the rock and carved out the cave's passages found today, according to NPS.

The exact length of Mammoth Cave is unknown, but explorers have mapped more than 426 miles (686 kilometers) of it, and are still uncovering new passages. It hosts a treasure trove of ancient fish fossils — more than 70 different long-lost species have been identified within its walls so far.

The latest find was extracted from the Ste. Genevieve rock formation and dates back to the Carboniferous period (358.9 million to 298.9 million years ago). The genus name, "Macadens," honors Mammoth Cave, while the species name, "olsoni," honors Rickard Olson, a retired park scientist who has played a key role in documenting these fossils, according to the statement.

The M. olsoni discovery helps researchers better understand the ancient ecosystems now preserved in Mammoth Cave, which may have once been similar to reefs.

"This finding not only enhances our knowledge of ancient marine ecosystems but also emphasizes the critical role of paleontological research in our national parks," Trimble said. "Every discovery connects the past with the present and offers invaluable educational opportunities for students and the public."

A mysterious "runner" dinosaur, only about the size of a dog, scurried around the ancient floodplains of what is now Colorado around 150 million years ago, a new study finds.

The two-legged herbivore, named Enigmacursor mollyborthwickae, was around 3 feet (1 meter) long and 1.5 feet (0.5 m) tall. However, despite its small stature, the discovery of this dinosaur is having a big impact on scientists' understanding of several Jurassic species.

A private fossil company excavated E. mollyborthwickae in Colorado between 2021 and 2022. The skeleton was later put up for sale, advertised as Nanosaurus, which is another type of small dinosaur from the same rock formation — called the Morrison Formation. After the Natural History Museum in London bought the skeleton, researchers found that not only is this new specimen not Nanosaurus, but the scientific classification of Nanosaurus and several other dinosaurs from the Morrison Formation are also unreliable.

The Morrison Formation is home to many iconic dinosaur fossils, such as the plated Stegosaurus and the ferocious predator Allosaurus, which would have lived alongside E. mollyborthwickae during the Jurassic period (201.3 million to 145 million years ago). The new study, published Wednesday (June 25) in the journal Royal Society Open Science, highlights that researchers still have a lot to learn about the formation's smaller dinosaurs.

"While the Morrison Formation has been well-known for a long time, most of the focus has been on searching for the biggest and most impressive dinosaurs," study co-lead author Susannah Maidment, a senior researcher at the Natural History Museum, said in an article published by the museum. "Smaller dinosaurs are often left behind, meaning there are probably many still in the ground."

Related: Meet 'Dragon prince' — the newly discovered T. rex relative that roamed Mongolia 86 million years ago

The skeleton was excavated by a company called Dinosaurs of America, LLC and acquired by the David Aaron art gallery in London, before the Natural History Museum purchased the fossils in 2024, according to the study. When the researchers got their hands on the alleged Nanosaurus, they began to look closely at the group, along with other small-bodied Morrison Formation dinosaurs.

"Nanosaurus wasn't named based on many fossilised bones, but largely the preserved impressions of bones pressed into hardened sand that are very difficult to study," study co-lead author Paul Barrett, a paleobiologist at the Natural History Museum, said in the museum's article. "So, we turned to the other bones that have been referred to the group over the past century, but these weren't particularly well-preserved either."

The fossil record for several small-bodied Morrison Formation dinosaurs is poor and incomplete, and it has undergone several scientific revisions, according to the study. Barrett and Maidment reviewed Nanosaurus and similar Morrison Formation species in a study published April 25 in the journal Bulletin of the Peabody Museum of Natural History, concluding that by modern standards, none of them had distinct enough features or a unique combination of characteristics to be valid.

For the new study, the researchers pored over the so-called Nanosaurus specimen and scanned it so they could create virtual 3D images of its fossilized bones. They determined that a unique combination of features, particularly in its legs, made the animal distinct enough from other dinosaurs. Their analysis found that its closest known relative was Yandusaurus hongheensis, a Jurassic herbivore from China.

Barrett and Maidment created a new genus (group) for the specimen. The genus name, Enigmacursor, combines the words "enigma" — a reference to the mysteries surrounding its scientific classification — and "cursor," which means "runner" in Latin. The dinosaur's species name, "mollyborthwickae," honors museum donor Molly Borthwick, whose donation allowed the Natural History Museum to purchase the specimen, according to the study. The museum didn't disclose the cost of the specimen.

"By studying its anatomy in detail, we've been able to clarify this species' evolutionary relationships, its taxonomy and the diversity of a previously poorly understood group of small dinosaurs," Maidment said in a statement.

About 66 million years ago — perhaps on a downright unlucky day in May — an asteroid smashed into our planet.

The fallout was immediate and severe. Evidence shows that about 70% of species went extinct in a geological instant, and not just those famous dinosaurs that once stalked the land. Masters of the Mesozoic oceans were also wiped out, from mosasaurs — a group of aquatic reptiles topping the food chain — to exquisitely shelled squid relatives known as ammonites.

Even groups that weathered the catastrophe, such as mammals, fishes and flowering plants, suffered severe population declines and species loss. Invertebrate life in the oceans didn't fare much better.

But bubbling away on the seafloor was a stolid group of animals that has left a fantastic fossil record and continues to thrive today: bivalves — clams, cockles, mussels, oysters and more.

What happened to these creatures during the extinction event and how they rebounded tells an important story, both about the past and the future of biodiversity.

Surprising discoveries on the seafloor

Marine bivalves lost around three-quarters of their species during this mass extinction, which marked the end of the Cretaceous Period. My colleagues and I — each of us paleobiologists studying biodiversity — expected that losing so many species would have severely cut down the variety of roles that bivalves play within their environments, what we call their "modes of life."

But, as we explain in a study published in the journal Sciences Advances, that wasn't the case. In assessing the fossils of thousands of bivalve species, we found that at least one species from nearly all their modes of life, no matter how rare or specialized, squeaked through the extinction event.

Statistically, that shouldn't have happened. Kill 70% of bivalve species, even at random, and some modes of life should disappear.

Related: The 5 mass extinction events that shaped the history of Earth — and the 6th that's happening now

Most bivalves happily burrow into the sand and mud, feeding on phytoplankton they strain from the water. But others have adopted chemosymbionts and photosymbionts — bacteria and algae that produce nutrients for the bivalves from chemicals or sunlight in exchange for housing. A few have even become carnivorous. Some groups, including the oysters, can lay down a tough cement that hardens underwater, and mussels hold onto rocks by spinning silken threads.

We thought surely these more specialized modes of life would have been snuffed out by the effects of the asteroid's impact, including dust and debris likely blocking sunlight and disrupting a huge part of the bivalves' food chain: photosynthetic algae and bacteria. Instead, most persisted, although biodiversity was forever scrambled as a new ecological landscape emerged. Species that were once dominant struggled, while evolutionary newcomers rose in their place.

The reasons some species survived and others didn't leave many questions to explore. Those that filtered phytoplankton from the water column suffered some of the highest species losses, but so did species that fed on organic scraps and didn't rely as much on the Sun's energy. Narrow geographic distributions and different metabolisms may have contributed to these extinction patterns.

Biodiversity bounces back

Life rebounded from each of the Big Five mass extinctions throughout Earth's history, eventually punching through past diversity highs. The rich fossil record and spectacular ecological diversity of bivalves gives us a terrific opportunity to study these rebounds to understand how ecosystems and global biodiversity rebuild in the wake of extinctions.

The extinction caused by the asteroid strike knocked down some thriving modes of life and opened the door for others to dominate the new landscape.

While many people lament the loss of the dinosaurs, we malacologists miss the rudists.

These bizarrely shaped bivalves resembled giant ice cream cones, sometimes reaching more than 3 feet (1 meter) in size, and they dominated the shallow, tropical Mesozoic seas as massive aggregations of contorted individuals, similar to today's coral reefs. At least a few harbored photosymbiotic algae, which provided them with nutrients and spurred their growth, much like modern corals.

Today, giant clams (Tridacna) and their relatives fill parts of these unique photosymbiotic lifestyles once occupied by the rudists, but they lack the rudists' astonishing species diversity.

Mass extinctions clearly upend the status quo. Now, our ocean floors are dominated by clams burrowed into sand and mud, the quahogs, cockles and their relatives — a scene far different from that of the seafloor 66 million years ago.

New winners in a scrambled ecosystem

Ecological traits alone didn't fully predict extinction patterns, nor do they entirely explain the rebound. We also see that simply surviving a mass extinction didn't necessarily provide a leg up as species diversified within their old and sometimes new modes of life — and few of those new modes dominate the ecological landscape today.

Like the rudists, trigoniid bivalves had lots of different species prior to the extinction event. These highly ornamented clams built parts of their shells with a super strong biomaterial called nacre — think iridescent pearls — and had fractally interlocking hinges holding their two valves together.

But despite surviving the extinction, which should have placed them in a prime position to accumulate species again, their diversification sputtered. Other types of bivalves that made a living in the same way proliferated instead, relegating this once mighty and global group to a handful of species now found only off the coast of Australia.

Lessons for today's oceans

These unexpected patterns of extinction and survival may offer lessons for the future.

The fossil record shows us that biodiversity has definite breaking points, usually during a perfect storm of climatic and environmental upheaval. It's not just that species are lost, but the ecological landscape is overturned.

Many scientists believe the current biodiversity crisis may cascade into a sixth mass extinction, this one driven by human activities that are changing ecosystems and the global climate. Corals, whose reefs are home to nearly a quarter of known marine species, have faced mass bleaching events as warming ocean water puts their future at risk. Acidification as the oceans absorb more carbon dioxide can also weaken the shells of organisms crucial to the ocean food web.

Findings like ours suggest that, in the future, the rebound from extinction events will likely result in very different mixes of species and their modes of life in the oceans. And the result may not align with human needs if species providing the bulk of ecosystem services are driven genetically or functionally extinct.

The global oceans and their inhabitants are complex, and, as our team's latest research shows, it is difficult to predict the trajectory of biodiversity as it rebounds — even when extinction pressures are reduced.

Billions of people depend on the ocean for food. As the history recorded by the world's bivalves shows, the upending of the pecking order — the number of species in each mode of life — won't necessarily settle into an arrangement that can feed as many people the next time around.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Scientists have identified a never-before-seen species of dinosaur called the dragon prince — a prehistoric predator that set tyrannosaurs on the path to ruling Earth. This newly discovered relative of Tyrannosaurus rex came to light after researchers re-examined fossils found in Mongolia.

Its existence sheds light on the story of tyrannosaur dinosaurs and how they evolved and spread.

The scientists named the dinosaur the dragon prince of Mongolia (Khankhuuluu mongoliensis), with the genus name based on the Latinization of the Mongolian words for prince and dragon. Their findings were published Wednesday (June 11) in the journal Nature.

"They [tyrannosauroids] were the princes before they took the mantle of kingship," study co-author Jared Voris, a researcher at the University of Calgary in Canada, told Live Science.

Tyrannosauroids were giant apex predators that walked on two legs, had huge heads with sharp teeth and tiny arms. They are part of the larger tyrannosauroid family and were thought to have evolved from smaller species — but until now there has been little fossil evidence to support this idea.

So, Voris set out for Mongolia to examine partial tyrannosauroid skeletons that had been excavated decades ago but not yet fully examined.

Related: Dinosaurs might still roam Earth if it weren't for the asteroid, study suggests

"Many of us in the palaeontology community knew that these Mongolian fossils were lurking in museum drawers, waiting to be studied properly, and apt to tell their own important part of the tyrannosaur story," Steve Brusatte, a palaeontologist and evolutionary biologist at the University of Edinburgh, U.K., who wasn't involved in the research, told Live Science.

The specimens that really caught Voris' eye were found in Mongolia in 1972 and 1973 and described in a scientific paper in 1977, when the individuals were identified as the already known genus Alectrosaurus.

But after being reexamined, "I realized it was something completely different than anything we'd ever seen," Voris said. "And it actually represented the ancestor of all of our big apex predatory tyrannosaurs that we find both here in Alberta and in Mongolia and China."

The dragon prince lived 86 million years ago and looked much like a tyrannosaur, but it was only about 13 feet (4 meters) long, weighing in at 1,650 pounds (750 kilograms). Many later tyrannosaurs were much bigger, with T. rex reaching 41 feet (12.5 m) long and weighing up to about 23,000 pounds (10,400 kg). The dragon prince also had a smaller head and longer arms compared to later tyrannosaurs.

"It's a nice new discovery giving us a better sense of what this intermediate phase of tyrannosaur history is like," Thomas Holtz, a vertebrate paleontologist at the University of Maryland, who wasn't part of the team, told Live Science.

Voris thinks the specimens are small adult individuals, rather than young dinosaurs. He identified a slew of features that are indicators of maturity, including fused-up vertebrae, prominently developed small horns and the nasal bone having a wrinkled texture. "The size is representative of the actual species rather than it being a younger animal," Voris said.

However, until a cross-section of the bones is done to look at growth rings, which hasn't yet been permitted because of the rare status of the fossils, we can't be sure of this adult status, Holtz said.

Unlike later tyrannosaurs, K. mongoliensis probably didn't hunt sauropods, the huge herbivorous dinosaurs with the long necks and long tails, said study co-author Darla Zelenitsky, a paleontologist at the University of Calgary. "It was probably taking down prey smaller than itself," Zelenitsky told Live Science.

The finding suggests that tyrannosauroids were still small at the time, and only later became giants.

"What makes the specimens so important is their age. They are about 86 million years old, a good 20 million years older than T. rex," Brusatte said. "It shows that tyrannosaurs were still relatively small at this time, and only later did they become colossal."

The researchers also compared 12 species of tyrannosaurs to figure out when and where they lived, how they were related, and when any migrations might have taken place.

They found that, about 85 million years ago, K. mongoliensis, or a closely related species, migrated out of Asia into North America across a land bridge where the Bering Strait is now and gave rise to the first true tyrannosaurs. These went on to be the dominant predators in North America in the latter part of the Cretaceous period between about 85 million and 66 million years ago.

But about 78 million years ago, a tyrannosaur migrated back across the land bridge, resulting in their first appearance in Asia.

This resulted in the evolution of two tyrannosaur subgroups in Asia: huge ones weighing several tons like Tarbosaurus bataar, and smaller, slim ones such as Qianzhousaurus sinensis, which was nicknamed "Pinocchio rex" because of its small size and long snout.

During a third migration, about 68 million years ago, one of the giant tyrannosaur species from Asia traveled back to North America and probably gave rise to T. rex, Zelenitsky said.

"They show that a few big migration events back and forth between Asia and North America were the drivers of much of tyrannosaur evolution," Brusatte said. "The tyrannosaur family tree was shaped by migration, just like so many of our human families."

Birds have been nesting in rugged Arctic environments for almost 73 million years, new research finds — more than 25 million years longer than was previously thought.

A collection of more than 50 fossils found in northern Alaska, which include embryos and hatchlings, suggest some of the early ancestors of modern birds either migrated or adapted to the harsh polar environment in the Mesozoic era, the age of dinosaurs.

"The common conception is they're too primitive to be exhibiting this advanced behavior," Lauren Wilson, lead author of the study and a doctoral student of paleontology at Princeton University, told Live Science. "So you're either dealing with [Arctic winters] as an itty-bitty, freshly hatched bird, or you're 3 months old, and having to fly about 2,000 kilometers [1,240 miles] to get to a point where it makes sense to even migrate," Wilson explained. "I don't think we would expect either of those things from these birds that don't belong to that modern lineage of birds."

Whether the birds migrated south or hunkered down for the winter, the research provides the earliest known evidence of either behavior in birds. And while some modern birds, like the ivory gull (Pagophila eburnea) and snowy owl (Bubo scandiacus) are known to nest in the frigid Arctic, there is now evidence that this behavior started millions of years before the meteor that wiped out non-avian dinosaurs crashed into Earth, if not earlier.

"Many birds nest in the Arctic today, and they are key parts of Arctic communities and ecosystems and food webs," Steve Brusatte, a professor of paleontology and evolution at the University of Edinburgh who peer-reviewed the study but was not involved in it, told Live Science in an email. "These fossils show that birds were already integral parts of these high latitude communities many tens of millions of years ago, and thus that these communities are a long-term norm of Earth history, not a recent ecological innovation of modern times."

The fossils in the collection come from at least three different families of bird: the extinct, loon-like hesperornithes; ichthyornithes, an extinct bird that resembled seagulls; and several species resembling ducks that are within or very similar to neornithes, the group containing all modern birds.

Related: Hoatzin: The strange 'stinkbird' born with clawed wings that appears to be an evolutionary 'orphan'

Notably, the researchers did not find any fossils of the dominant bird group of the Cretaceous period (145 million to 66 million years ago) — enantiornithes, now-extinct birds that typically had teeth in their beaks and claws on their wings. But a few factors reveal why they likely didn't live in the Arctic. They likely took longer than other birds to incubate their eggs, they took several years to reach full adult size (where most modern birds grow to adult size within weeks) and they "may have had a period where they're almost naked because they molted their feathers simultaneously," which is not helpful during an Arctic winter, said study co-author Daniel Ksepka, a paleontologist and curator of the Bruce Museum in Connecticut.

The world was warmer in the Late Cretaceous than it is today, but the region the birds were found in likely experienced freezing temperatures, snow and roughly four straight months of winter darkness. Growing to adulthood so quickly allowed modern birds to practice long-range migration and prosper during those ancient Arctic summers, which boasted around six months of 24-hour daylight and a burst in insect populations.

But the weather wasn't the only challenge. They lived alongside "probably about 12 or 13 different kinds of typical dinosaurs," like the Pachyrhinosaurus, a relative of Triceratops that was about 16 feet (5 meters) long and weighed 2 tons (1,800 kilograms). Other dinosaurs like Troodon, an 11-foot tall meat-eater with short, serrated teeth, "would have happily taken advantage of a bunch of these little cute little chicks for dinner," said Patrick Druckenmiller, director of the University of Alaska Museum of the North and advising author of the study.

To get to the fossil sites in the Prince Creek Formation in Northern Alaska, the researchers drove 500 miles (800 km) from Fairbanks, chartered a small aircraft to fly to the Colville River, then took inflatable motorboats up the river before setting up camp, Druckenmiller said. There they would look for an "orangey, pebbly, sandy" layer of sediment that contains small bones and teeth, and often lay on the permafrost to "excavate with little dental picks and small tools" from the layer itself.

Now that the Prince Creek Formation is "one of the major North American Cretaceous bird sites," according to the researchers, Wilson says the next step is simply to find more fossils.

"The more bones we find, the more confident we can be in exactly what types of birds we have," she said. "We might even still find a random bone that's from a bird we didn't know was there."

Bird quiz: How much do you know about our feathered friends?

Bones from an extinct human ancestor have been recovered from the seafloor, revealing a previously unknown Homo erectus population in Southeast Asia that may have interacted with more modern humans, new studies find.

The H. erectus bones were among a cache of more than 6,000 animal fossils hoovered up as part of a construction project off the island of Java in Indonesia. This is the first time scientists have seen fossils from the submerged parts of the Indonesian archipelago, which connected islands like Java to the Asian mainland during the last ice age, when sea levels were lower.

These lost lands, called drowned Sundaland, were once vast open plains interspersed with rivers around 140,000 years ago. The newly discovered fossils revealed the rivers were teeming with fish, turtles, river sharks, hippos and other marine life, while terrestrial giants such as elephants, the elephant-like Stegodon and water buffalo populated the plains, according to the studies.

H. erectus' presence on this landscape confirms that our ancient ancestor was taking advantage of drowned Sundaland's fertile hunting grounds, at least between Java and another, smaller island called Madura. This region, once a valley, is now submerged in a body of seawater called the Madura Strait.

The researchers found cut marks on some of the fossils that confirmed the Madura Strait hominins (humans and our close relatives) were hunting turtles — the earliest evidence of this in Southeast Asia — and large game. The remains also suggested that these hominins were selectively targeting cow-like bovids in their prime, which Indonesian H. erectus isn't known for. This hunting strategy is associated with more modern humans on the Asian mainland, raising the possibility that the newly discovered H. erectus population copied the strategy from other human relatives.

"The Madura Strait hominins may have developed this hunting strategy independently," study lead author Harold Berghuis, a researcher studying H. erectus at Leiden University in the Netherlands, told Live Science in an email. "But the other possibility is that we are looking at a kind of cultural exchange."

The researchers shared their findings in four separate studies published last week in the journal Quaternary Environments and Human.

Related: Ancient quarries in Israel reveal where Homo erectus hunted and butchered elephants

H. erectus is an important part of our evolutionary history. Emerging at least 2 million years ago, it was the first species to develop human-like body proportions and the first human species to migrate out of Africa, eventually finding its way to Southeast Asia. Other ancient humans followed in H. erectus' footsteps, but the extent to which these different species interacted in Southeast Asia is unknown, and the genetics of these different hominins is uncertain.

The human family tree is complicated, particularly in Southeast Asia. Berghuis noted that by around 350,000 years ago, H. erectus was being replaced on what is now the Asian mainland by a more modern human population, which included the mysterious Denisovans and the Neanderthals.

Fossil evidence suggests that H. erectus continued to survive on the island of Java until around 117,000 to 108,000 years ago, when the species eventually went extinct. Our species, H. sapiens, arrived in Southeast Asia around 77,000 years ago.

Fossil island dream

The latest fossil discovery was uncovered because of a large construction project in the Madura Strait. From 2014 to 2015, contractors pulled around 177 million cubic feet (5 million cubic meters) of sand and sandstones from the seabed near the port city of Surabaya to create an artificial island, according to one of the new studies published May 15.

To remove the sediment, the contractors used a trailing suction hopper dredger, which is a ship that drags a steel structure along the seabed, breaking up the sediment and mixing it with water. A suction pipe then hoovered up the sediment. This process, called dredging, can negatively impact marine life, but the amount of damage varies depending on the location and the species involved — invertebrates, eggs and larvae are most vulnerable to the practice. Berghuis noted that under Indonesian legislation, the dredging was subject to environmental impact assessments and supervision.

The hoovered-up sediment was discharged at a land reclamation site to create a 250-acre (100 hectare) sandy island. Berghuis had access to the site as a geotechnical consultant for the port of Surabaya, and spent many weeks searching on hands and knees for fossils. He told Live Science that he "dreamed" of finding a hominin fossil, but it wasn't until his very last day of collecting that he finally spotted one.

"It was already getting dark and I sat down to enjoy [the] sunset," Berghuis said. "And then, right beside me, lay this fossil that reminded me so much of the only Dutch Neanderthal. This is a well-known fossil in my country, dredged from the North Sea."

Berghuis took the fossil, a skull fragment, back to his hotel room and compared it with images of the famous Dutch Neanderthal. Its pronounced brow ridge was similar to Neanderthals and other ancient humans. Berghuis and his colleagues later determined it belonged to an adult or adolescent H. erectus.

The team also identified another H. erectus skull fragment in the fossils Berghuis recovered. Based on the thickness of the second fragment, the team determined this individual had not reached adulthood, according to one of the studies. The researchers couldn't determine how the individuals died.

Related: When did modern humans reach each of the 7 continents?

Land of dragons

The H. erectus discovery was just the tip of a mountain of findings documented in the new studies. Researchers identified 36 different species in a total of 6,372 recovered fossils. These included fossils of Komodo dragons (Varanus komodoensis).

Komodo dragons are giant lizards capable of (slowly) killing large animals, including water buffalo, with bacteria and venom-laced bites. Today, they are an endangered species restricted to a few Indonesian islands, but the new studies suggest they could have ruled the Sundaland plains.

"Komodo dragons may have been the most important predators," Berghuis said.

Half a billion years ago, a feisty predator flapped around the primordial seas, hooking prey into its mouth while breathing through long gills on its butt.

Researchers recently discovered this 506 million-year-old creature, called Mosura fentoni, in a cache of museum fossils in Canada. The fossils suggest that these early arthropods were more diverse than previously thought. The team thinks the now-extinct arthropod would have looked a bit like a moth — a distant living cousin — so they named it after Mothra, the fictional giant moth from Japanese cinema.

Whereas Mothra is large enough to battle Godzilla on the silver screen, the real-life M. fentoni was only about the size of a human finger. Despite its small size, this tiny creature represents a huge and rare find for scientists.

The M. fentoni fossils, plucked mostly from the Burgess Shale rock formation in the Canadian Rockies, are so well preserved that they include intricate details of the species' biology, including the creature's nervous system, circulatory system and digestive tract. This is extremely rare for fossils, which scarcely preserve soft tissues, and helps shed light on the evolution of ancient arthropods.

"Very few fossil sites in the world offer this level of insight into soft internal anatomy," study co-author Jean-Bernard Caron, the Richard M. Ivey curator of invertebrate paleontology at the Royal Ontario Museum, said in a statement. "We can see traces representing bundles of nerves in the eyes that would have been involved in image processing, just like in living arthropods. The details are astounding."

The researchers published their findings Wednesday (May 14) in the journal Royal Society Open Science.

Related: Scientists uncover 'inside-out, legless, headless wonder' that lived long before the dinosaurs

Arthropods are a large group of invertebrates with hard exoskeletons, segmented bodies and jointed legs. Today, they make up around three-quarters of all living animals, including insects, arachnids and crustaceans. One of the reasons for their evolutionary success is their specialized body segments. These variable segments have helped arthropods diversify within their groups and ultimately become everything from horseshoe crabs to moths.

M. fentoni belonged to a group of ancestral arthropods called radiodonts, identifiable by shared features like side flaps and head appendages. These invertebrates thrived during the Cambrian period (541 million to 485 million years ago), but their fossils have shown relatively uniform body segments with little variety, until now.

Researchers collected 60 fossils of the newly described species between 1990 and 2022, primarily from the Raymond Quarry, part of Yoho National Park in British Columbia. Many of these specimens had been sitting in the Royal Ontario Museum for years until the authors of the new study took a closer look at them. The team also identified one other specimen in the Smithsonian National Museum of Natural History in Washington, D.C., according to the study.

"Museum collections, old and new, are a bottomless treasure trove of information about the past," study lead author Joe Moysiuk, curator of paleontology and geology at the Manitoba Museum, said in the statement. "If you think you've seen it all before, you just need to open up a museum drawer."

The researchers photographed and scanned the fossils to build a picture of this ancient creature's biology. They found that, unlike other radiodonts, M. fentoni had lots of body segments on its rear, which were lined with gills. The species also had the longest gills relative to body length of all known radiodonts, despite being among the smallest, according to the study.

The team concluded that the back-end gills were most likely a specialized system for respiration; horseshoe crabs, wood lice and some other living arthropods have subsequently evolved a similar system. Researchers aren't certain why M. fentoni needed the long butt gills, but they speculated it was an adaptation to low-oxygen environments or an active lifestyle — possibly a very active reproductive lifestyle — that required greater oxygen consumption. Either way, the discovery highlights that radiodonts were more diverse than previously thought.

"Radiodonts were the first group of arthropods to branch out in the evolutionary tree, so they provide key insight into ancestral traits for the entire group," Caron said. "The new species emphasizes that these early arthropods were already surprisingly diverse and were adapting in a comparable way to their distant modern relatives."

Reptiles as we know them today may have evolved about 30 million years earlier than we initially assumed, new footprints reveal.

According to a study published Wednesday (May 14) in the journal Nature, fossilized tracks found in Australia may have been left by the clawed feet of a small reptile-like creature about 350 million years ago, during the Carboniferous period.

This new discovery would push back the evolution of these animals by roughly 30 million years, as early reptiles were previously thought to have evolved around 320 million years ago.

"Once we identified this, we realised this is the oldest evidence in the world of reptile-like animals walking around on land — and it pushes their evolution back by 35-to-40 million years older than the previous records in the Northern Hemisphere," study co-author John Long, a strategic professor of palaeontology at Flinders University in Australia, said in a statement.

"The implications of this discovery for the early evolution of tetrapods are profound."

Modern reptiles, along with birds and mammals, are part of a group of animals known as amniotes, which are defined as tetrapod vertebrates (four-limbed animals with backbones) that lay eggs equipped with a protective membrane that surrounds the embryo. This so-called amnion allows eggs to be laid on land, freeing early land animals from dependency on water for reproduction. This is in contrast to amphibians, which rely on moist environments to reproduce.

Related: Which animal species has existed the longest?

Amniotes evolved from amphibian-like ancestors, with the earliest amniote body fossils being dated to the late Carboniferous Period, which spanned from approximately 359 to 299 million years ago. These early amniotes, which were small, lizard-like creatures, then diversified into two groups: synapsids and sauropsids, which evolved into the earliest ancestors of mammals and reptiles, respectively.

Based on the fossil record, amniotes were thought to have evolved around 320 million years ago. However, this new discovery of clawed amniote footprints in Australia from 350 million years ago throws these estimations hugely off.

"I'm stunned," study co-author Per Ahlberg, a professor of paleontology at Uppsala University, said in a statement. "A single track-bearing slab, which one person can lift, calls into question everything we thought we knew about when modern tetrapods evolved."

These footprints were discovered on a 20-inch (50cm) rock slab by two amateur palaeontologists in the Snowy Plains Formation in Australia's Victoria, which dates back to 350 million years ago. The footprints appeared to have been made by a creature with clawed feet and long toes, likely an early sauropsid, meaning that reptiles may have been around much earlier than we assumed.

"Claws are present in all early amniotes, but almost never in other groups of tetrapods," Ahlberg said. "The combination of the claw scratches and the shape of the feet suggests that the track maker was a primitive reptile."

These footprints are the earliest clawed prints ever discovered.

"When I saw this specimen for the first time, I was very surprised," study co-author Grzegorz Niedźwiedzki, a researcher at Uppsala University, said in the statement.

Pushing back the tree of reptilian evolution, the researchers concluded that reptiles may have actually evolved towards the end of the Devonian period, when primitive fish-like creatures like Tiktaalik roamed the land.

"It's all about the relative length of different branches in the tree," Ahlberg said. "In a family tree based on DNA data from living animals, branches will have different lengths reflecting the number of genetic changes along each branch segment. This does not depend on fossils, so it's really helpful for studying phases of evolution with a poor fossil record."

Niedźwiedzki added: "The most interesting discoveries are yet to come and that there is still much to be found in the field. These footprints from Australia are just one example of this."

Ancient tracks reveal that many pterosaurs were just as comfortable walking on the ground as they were flying through the skies during the age of dinosaurs, a new study finds.

Pterosaurs, informally called "pterodactyls," were flying reptiles that ruled the skies when dinosaurs dominated the land. However, new research has discovered that pterosaurs diversified during the middle of the Jurassic period (201 million to 145 million years ago) and evolved to walk more effectively on four limbs, using their hands and feet.

The findings were published May 1 in the journal Current Biology, and support decades-old evidence from the fossil record. Researchers also matched previously unidentified tracks to specific pterosaur groups, offering a new window into their lives.

"Footprints offer a unique opportunity to study pterosaurs in their natural environment," study lead author Robert Smyth, a doctoral researcher at the University of Leicester in the U.K., said in a statement. "They reveal not only where these creatures lived and how they moved, but also offer clues about their behaviour and daily activities in ecosystems that have long since vanished."

Related: 'Sexy' pterosaur tail should have been nightmare for flying. How did it work?

Many pterosaur studies have focused on their flight and feeding. However, researchers have uncovered many fossilized pterosaur tracks in recent decades, which represent a unique and untapped resource, according to the study.

The problem with pterosaur tracks — or any other extinct animal tracks — is that it's difficult for researchers to know which species or group left them behind. Fossilization is rare, and researchers typically don't find bones and tracks alongside each other, which fossilize under different conditions.

For the new study, researchers created 3D models of pterosaur tracks and compared them with different pterosaur skeletons. They identified three distinct pterosaur track types and linked them to three known groups: ctenochasmatoids, dsungaripterids and neoazhdarchians. The neoazhdarchian group included Quetzalcoatlus northropi, one of the largest pterosaurs — and largest flying animals — to ever live.

They used this analysis to show that neoazhdarchian footprints were present in coastal and inland regions, suggesting that the animal was often on the ground, living in the same environments as dinosaurs, according to the statement.

Looking again through the magnifying lens at the fossil's surface, one of us, Sabrina Curran, took a deep breath. Illuminated by a strong light positioned nearly parallel to the surface of the bone, the V-shaped lines were clearly there on the fossil. There was no mistaking what they meant.

She'd seen them before, on bones that were butchered with stone tools about 1.8 million years ago, from a site called Dmanisi in Georgia. These were cut marks made by a human ancestor wielding a stone tool. After staring at them for what felt like an eternity − but was probably only a few seconds − she turned to our colleagues and said, "Hey … I think I found something."

What she'd spotted in 2017 was our team's first evidence that hominins butchered several animals at the site of Grăunceanu, in Romania, at least 1.95 million years ago. Before this discovery, those other cut marks from Dmanisi were the oldest well-dated evidence in Eurasia of the presence of hominins − our direct human ancestors.

Other scientists have reported sites in Eurasia and northern Africa with either hominin fossils, stone tools or butchered animal bones from around this time. Our recently published research adds to this story with well-dated, verified evidence that hominins of some kind had spread to this part of the world by around 2 million years ago.

Related: 150,000-year-old stone tools reveal humans lived in tropical rainforests much earlier than thought

Romanian site with fossilized animal bones

A little background on Grăunceanu: This open-air site was originally excavated in the 1960s, and researchers found thousands of fossil animal bones there. It's one of the best-known Early Pleistocene sites in East-Central Europe. Many of the fossil animal bones are quite complete and at the time of excavation lay together as they were positioned in life. The original deposition was called a "bone nest" because of how densely packed the bones were.

If you were to stand on the hillside surrounding Grăunceanu almost 2 million years ago, it would likely have seemed familiar: a river channel surrounded by a forest that fades into more open grasslands to the foothills. Occasionally that river floods its banks, inundating the valley with rich soils, providing nutrients for the plants that the resident animals feed on. All pretty familiar, until you look more closely at those animals: ostriches, pangolins, giraffes, saber-toothed cats and hyenas − in Europe!

It's the fossil bones of these ancient animal inhabitants that were excavated at Grăunceanu. Unfortunately, most of the excavation records and provenance data for the site have been lost. Even without those, though, the Grăunceanu fossils are so remarkably preserved that they offer up a wealth of paleontological information.

A few years after finding those first cut marks, our team, including biological anthropologist Claire Terhune, zooarchaeologist Samantha Gogol, and paleoanthropologist Chris Robinson, spent several weeks carefully studying all 4,524 Grăunceanu fossils, looking for more marks.

We examined all surfaces of every fossil bone with a magnifying lens and low-angled light. Most of these fossils have root etching on them − sinuous, shallow, overlapping marks made by plant roots that grew nearby. But whenever we saw a linear mark that looked interesting, we took an impression of that mark with dental molding material.

Confirming they're cut marks

We can't go back in a time machine to watch when these marks were made. Yes, ancient human butchers wielding stone tools would leave marks on bone. But mammalian predators or crocodiles could also leave marks with their sharp teeth. Sediments in rivers could scratch any bones rolling around in the water. Large animals walking across the landscape could move and scrape bones with their steps.

So how can we be confident that they're cut marks? That's where our zooarchaeologist collaborators Michael Pante and Trevor Keevil came in.

Within the past decade, Pante developed a novel method for identifying the source of marks left on bones. The first step is capturing precise 3D measurements of the mark impressions using an advanced microscope called a noncontact 3D optical profiler.

Then they compare the 3D shape data from the ancient marks with a reference set of 898 marks on modern bones made by known processes, including stone tool butchery, carnivore feeding and sedimentary abrasion.

This new method adds to the more qualitative, descriptive criteria many researchers, including our team, use to make mark identifications. For instance, we consider things such as mark location: Is the mark near a muscle attachment site, where you might expect to find a cut mark if a hominin were removing meat from a bone?

Based on our analyses, we determined that 20 Grăunceanu fossils are marked by cuts, with eight displaying high-confidence cut marks. Most of those marks are on fossils of hoofed animals, including a few deer; one is a small carnivore leg bone. When we could identify the type of bone, the cut marks are always in anatomical locations consistent with cutting meat off bones.

Dating the site

While the fossil species present can give us a rough age estimate of the site, we used uranium-lead (U-Pb) dating to get more precise age information. This technique relies on the fact that naturally occurring uranium decays over long but well-known periods of time to eventually transform into lead. Geologists use the ratio of these two elements like a radiometric clock to determine how old something is.

When one of us, Virgil Drăgușin, asked geochemist Jon Woodhead to use U-Pb dating to estimate the age of the Grăunceanu fossils based on several small tooth fragments, he was reluctant. Teeth do not usually work well for this dating technique. But he agreed to a test run, and to his surprise the teeth he tried worked very well.

Together with his colleague John Hellstrom, they calculated a much more precise date for the site. We now know the Grăunceanu site is older than 1.95 million years.

All of this data together − the very well-calibrated and tightly clustered dates of the specimens plus at least 20 cut-marked bones verified both by qualitative and quantitative methods − provides very reliable evidence that hominins were indeed in Eurasia by at least 1.95 million years ago, even though there are no hominin fossils from Grăunceanu.

Sometimes when we look through our magnifying lenses, it almost feels like we can peer into the past. That's impossible − but we can piece together lines of evidence to paint a clearer picture of what happened in the past at Grăunceanu.

Now, imagining the view 1.95 million years ago, we see scenes of deer cautiously drinking from the river, majestic mammoths in the distance, a herd of horses grazing, a saber-toothed cat stalking a large monkey, a bear teaching her cubs to hunt … and a small group of hominins butchering a deer.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Fossilized footprints on the Isle of Skye in Scotland have revealed that a variety of dinosaurs once stalked the island's prehistoric landscape.

New research, published April 2 in the journal PLOS One, describes 131 footprints made by dinosaurs that traversed lagoons during the Bathonian age (168.3 million to 166.1 million years ago) of the Middle Jurassic. The location, now called Prince Charles' Point, is named for Prince Charles Edward Stuart — known as Bonnie Prince Charlie — because he supposedly landed there following his defeat in the Battle of Culloden in 1746.

Traces left in wet sediments offer paleontologists unique insights into the lives of extinct animals, including the environments they inhabited, their size and even social habits.

The set of tracks discovered on Skye show the movements of at least two dinosaur species — one a theropod, from the group that includes predators such as Tyrannosaurus rex, the other a sauropod, from the group of long-necked plant-eaters like Brontosaurus.

Related: 166 million-year-old fossil found on Isle of Skye belongs to pony-size dinosaur from Jurassic

Sixty-five of the tracks were recorded as belonging to theropods and 58 to sauropods. Eight were unidentified. In the case of the theropods, even impressions of their claws were preserved. Fossilized bones from both groups of dinosaur have previously been discovered on the Isle of Skye.

The theropod footprints show distinct impressions of three toes, while the sauropod footprints are circular. They are likely to belong to relatives of the carnivorous Megalosaurus (the first dinosaur ever named) and herbivorous Cetiosaurus, respectively.

Four similar but distinct types of theropod footprint were identified. "It's not impossible to postulate that more than one species of theropod was responsible for making a very similar type of footprint," lead author Tone Blakesley, a paleontology graduate student at the University of Edinburgh when the discovery was made, told Live Science.

Some of the individual sets of tracks extend up to 40 feet (12 meters). They range in size from 9.8 to 23.6 inches (25 to 60 centimeters). Their patterns suggest that the dinosaurs were engaged in milling behavior — random, undirected motion.

Previous discoveries on the island have found tiny footprints, which suggests breeding locations. No such imprints were found on Prince Charles' Point. It is unclear why the dinosaurs frequented the lagoon, which may have provided food or shelter.

The sauropod prints found there had previously been identified as fish burrows during the 1980s. Blakesley and his colleagues visited the site in 2019 and determined that they were actually dinosaur footprints after spotting a three-toed impression.

"Just as we were packing up because the tide was coming in, we found a theropod footprint," Blakesley recounted. "This is what happens in paleontology — you pack up and leave, then you find the best thing."

A distinctive set of conditions allowed the prints to be preserved. The researchers believe they were made in the sands of a very shallow lagoon. The light currents that passed through the water left ripples in the sand, still discernible in the sandstone in which the tracks are imprinted.

"They were walking around in a shoreline environment, a very shallow layer of water sitting on top of a very thin layer of sand," Blakesley explained. "The sand was strong enough to retain the shape of their feet."

When the water level rose, further sediment was deposited on top of the footprint in relatively short order — possibly by a storm. Even finer sediment was later layered on top, covering the tracks until it was eventually eroded, allowing the researchers to spot them.

"You would have to have a very quick burial of these footprints in order for them to be preserved so crisply," Blakesley noted.

The tracks are in an intertidal zone, meaning that they are constantly subjected to the action of waves. Their timely identification is crucial to study of dinosaurs on the island because they will eventually be washed away, erasing the traces left by the massive reptiles that once inhabited the region.

A CT scan of an ancient marine reptile that was entombed while pregnant has revealed a huge surprise — there were two fetuses inside her fossilized remains.

"Twins! She has another baby," Judith Pardo-Pérez, a paleontologist at the University of Magallanes in Chile who first discovered the fossil in 2009, told Live Science, adding that she plans to release more details of this discovery in a forthcoming research paper.

Sixteen ago, researchers working in southern Chile's Torres del Paine National Park struck paleontological gold, unearthing the fossilized remains of a pregnant ichthyosaur — a dolphin-like predator that patrolled the seas for most of the Mesozoic era (252 million to 66 million years ago).

The ichthyosaur was preserved in exquisite detail, and included the approximately 6-inch-long (15 centimeters) skeleton of an unborn fetus, the researchers initially reported.

The fossil was first discovered in 2009 when Pardo-Pérez was working as a doctoral student. When she returned to the site a year later, she noticed unusual bones between the ribs of the main fossil, indicating the presence of a fetus — but it wasn't until 2022 that the pregnant ichthyosaur, dubbed Fiona, was fully excavated.

Now, Pardo-Pérez and colleagues have carried out a full analysis of the fossil. Their findings were published Feb. 25 in the Journal of Vertebrate Paleontology.

Related: The world's largest ichthyosaur may have just been discovered in the Swiss Alps

The ichthyosaur, which lived approximately 131 million years ago, is estimated to have been around 11.5 feet (3.5 meters) long. Its remarkable preservation is attributed to the rapid burial of the carcass in sediment, coupled with a lack of scavengers, likely due to low oxygen levels on the seafloor, according to the study. Researchers identified it as Myobradypterygius hauthali, a species previously known from other fragmentary remains.

This find represents the third instance of a pregnant ichthyosaur from the Cretaceous period (145 million to 66 million years ago), although pregnant ichthyosaurs dating to the Jurassic and Triassic periods have also been found. The fetus' vertebrae, measuring approximately 0.6 inches (1.5 cm) in height, are surprisingly large in proportion to Fiona's 11.5-foot length. The researchers feel that M. hauthali may have given birth to relatively large babies.

Although some earlier ichthyosaurs pushed their newborns out head first, Fiona's remains suggest otherwise. The orientation of the fetus inside Fiona suggests that, like many evolutionary "advanced" ichthyosaurs, M. hauthali delivered its young tail first, an adaptation also seen in modern dolphins and whales.

The researchers also uncovered Fiona's last meal: the remains of small fishes. This is a rare glimpse into the dietary habits of Cretaceous ichthyosaurs, as direct evidence of their meals is uncommon.

Pardo-Pérez is continuing to analyze the pregnant ichthyosaur and has performed a CT scan of the fossil, allowing her to observe the entire skeleton in greater detail. It was then that she discovered that the ichthyosaur was pregnant with twins, and she plans to publish a new study on these findings in the future.