Science word of the day: Coprolite

Pronunciation: KAHP'-ruh-lite

What it means: Coprolites are fossilized poop. Scientists have found coprolites from animals as diverse as fish, dinosaurs and saber-toothed cats. Teeth in the saber-toothed cat poop indicated that it had been eating baby sloths, which frankly feels a bit unfair from a creature with 11-inch-long (28 centimeters) teeth.

These fossils form when poop gets rapidly buried and mineralized instead of rotting away. Coprolites can be hard to match to the animal that produced them, but undigested bones and teeth in the fossilized poop can often provide clues to the kinds of animals that other animals eat.

How to use it in a sentence: If you're ever in a science museum and a volunteer, with a twinkle in their eye, asks you what you think a chunky, rock-looking thing is, the answer is always coprolite.

Can you crack our science word of the day puzzle, Chain Word?

On July 14, 2026, "Gus," one of the most complete specimens of Tyrannosaurus rex, went to an as yet unidentified buyer for US$50.1 million. This auction at Sotheby's set a record for most valuable fossil ever sold. Another dinosaur has entered the luxury collectibles market, a reminder that even Earth's deepest history can be sold to the highest bidder.

To paleontologists like me, however, a fossil like "Gus" — excavated from the Hell Creek Formation in South Dakota over three years starting in 2021 by commercial collector Thomas Heitkamp and his team — is not a trophy or a work of art. It is an irreplaceable scientific archive. Fossils preserve evidence of evolution, extinction, growth, disease, injury and ancient ecosystems. They are finite, nonsubstitutable records of life’s history on Earth.

Science depends on independent verification of claims and healthy debate. Researchers must be able to revisit specimens, test earlier conclusions and ask new questions.

But once a scientifically important fossil enters a private collection, access for researchers is no longer guaranteed. Collectors typically sequester their fossils in their homes. Even when privately owned specimens are loaned to museums, the owners can change their minds, ending access at any time. This issue is especially of note when it comes to Tyrannosaurus rex; a 2025 study found that while there were 61 T. rex fossils in public trusts at that time, 71 were privately held.

That is why the Society of Vertebrate Paleontology, of which I'm a long-term member and president-elect, has long argued that scientifically significant vertebrate fossils belong in the public trust, curated in museums and universities that preserve them permanently, make them available for research and share them with the public.

Finding a fossil

Supporters of commercial fossil sales often argue that without sales to private collectors, specimens like "Gus" would remain buried or erode away. They’re right about one thing: Discovery matters. Many extraordinary fossils have been found by ranchers, hikers, amateur collectors and commercial excavators. Paleontology is accessible to everyone who has an eye for observing nature — you don't need to be an expert with academic credentials to make an important discovery.

But discovery is only the beginning. A fossil's scientific value depends on careful documentation of where it was found, the rocks surrounding it, and the plants and animals preserved alongside it. Those details allow scientists to reconstruct ancient ecosystems, understand how an animal lived and died, and interpret how its remains became fossilized. When that contextual information is incomplete or lost, much of the fossil's scientific value is lost as well.

Yet even discovery, excavation and publication barely scratch the surface of a fossil's scientific importance. The greatest scientific value of a specimen often comes decades later, when researchers ask new questions and apply new technologies that earlier generations never imagined. A specimen that seems fully studied today may yield surprising new information tomorrow, but only if it is still available for study.

Delayed discoveries

Consider the iconic dinosaurs, including T. rex, Triceratops, Diplodocus and Stegosaurus, first collected more than a century ago. Early paleontologists could describe their shapes but had no way to dig deeper by peering inside the bones. Because those specimens were preserved in museum collections, later generations could revisit them with technologies that didn't exist when they were discovered.

Paleontologist Larry Witmer and his collaborators at Ohio University started using CT imaging 20 years ago to reconstruct the internal anatomy of historic dinosaur fossils without damaging them, based on how X-rays travel through specimens. Brain cavities, inner ears, air spaces, nerves and blood vessels became visible for the first time, revealing how dinosaurs balanced, heard, smelled and perceived their world.

Henry Fricke, Thomas Cullen and other geochemists have used isotopic signatures preserved in fossil teeth and eggshells to reconstruct dinosaur diets, migration patterns and body temperatures. This research has revealed how dinosaurs lived: what they ate, how they moved through ancient landscapes, and even how warm their bodies were.

More recently, molecular paleontologist Jasmina Wiemann and her collaborators have identified chemical traces preserved in fossil bone, eggshell and skin that reveal aspects of dinosaur biology unimaginable even a generation ago. Until now, paleontologists had no way to know details about metabolic rates and reproduction or the colors of skin, feathers and eggs.

In my own research I use microscopes to uncover the hidden stories preserved inside dinosaur bones and teeth. Thin sections of fossil bones reveal that dinosaurs grew more like mammals and birds than like oversized reptiles. Microscopic modifications to bones capture traces of ancient scavenging, and tiny signatures deep inside baby dinosaur bones indicate the moment of hatching.

None of these discoveries would have been possible if the original fossils had vanished into inaccessible private collections.

Shared natural heritage, on the auction block

Fossils are not static objects whose scientific value is exhausted once they are described. Their value grows as science advances, but only if future researchers can continue to examine the original specimens.

Of course, sometimes dinosaur fossils are rescued from obscurity through purchase and immediate deposition or donation to natural history museums. Some of the world's most important dinosaur fossils are accessible today because individuals, companies or organizations with the means to acquire extraordinary specimens recognized that they belong where scientists can continue to study them and where future generations can learn from them.

Purchasing a fossil in order to place it permanently in the public trust is fundamentally different from acquiring it as a private collectible: One expands access, the other leaves access uncertain.

But as fossil prices rise into the millions, museums increasingly cannot compete. The most significant fossils are no longer reliably entering public collections. Instead, they are becoming luxury assets whose market value supersedes their scientific value.

Dinosaurs belong to our shared natural heritage. They inspire wonder because they connect all of us to a world unimaginably older than our own. For me, the question raised by auctions like the one on July 14 of "Gus" is not who can afford to own these relics of the past. It is whether future generations have the chance to study and learn from them.

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

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

The first dinosaur found in Antarctica belonged to a group that included the largest animals ever to walk the planet, a new study finds.

A backbone from the 82 million-year-old giant was discovered more than 40 years ago, but at the time, researchers assumed it came from an ancient marine reptile. Now a new study, published June 29 in the journal Acta Palaeontologica Polonica, has revealed that it was actually a titanosaur — the group of long-necked sauropods that included the largest land animals on record.

"At first glance this appears to be an unremarkable fossil, but it holds an important place in the history of Antarctic exploration as the first dinosaur fossil found on the continent," study first author Paul Barrett, a paleontologist at the Natural History Museum in London, said in a statement.

While this fossil now holds the record for the first dinosaur fossil found in Antarctica, other dinosaur fossils were identified on the continent after its discovery, so it's not the only known Antarctic dinosaur. In fact, researchers have identified a variety of dinosaurs on Antarctica, with another sauropod fossil identified as a titanosaur in 2011.

The newly identified dinosaur was around 20 to 23 feet (6 to 7 meters) long. That's very small compared with the largest-known titanosaurs, which could grow up to 123 feet (37.5 m) long. However, as the fossil is just a fragment of a vertebra, researchers are unable to narrow down which species the Antarctic titanosaur belonged to, and it's possible that the individual was only a juvenile when it died.

Mike Thomson, a British Antarctic Survey geologist, found the fossil during an expedition to James Ross Island in 1985. The island, which has been the site of multiple dinosaur discoveries, is located off the northeastern Antarctic Peninsula, south of the 600-mile-wide (965 kilometers) Drake Passage that separates South America from Antarctica.

Antarctica is well known for its icy landscapes, but when titanosaurs roamed Earth, the continent was still attached to South America and full of temperate forests. Antarctica's dinosaurs were so far south that they would have lived in constant twilight during the winter months, according to a news article published by the Natural History Museum.

The authors of the new study identified the dinosaur using high-resolution CT scans, which enabled them to look inside the fossil. Dating back to the Cretaceous period (143 million to 66 million years ago), the titanosaur lived in the last age of the non-avian dinosaurs, before an enormous asteroid hit what is now Mexico's Yucatan Peninsula 66 million years ago and wiped them out.

The Antarctic titanosaur helps researchers better understand how dinosaurs spread across Earth's southern continents, which at the time were combined into a supercontinent called Gondwana. The presence of titanosaurs on Antarctica suggests that they may have used Antarctica to travel from what is now South America to New Zealand.

Other dinosaurs identified on Antarctica include small herbivores, armored ankylosaurs and bipedal predators like Imperobator, which would have shared the forests with the newly identified titanosaur. While researchers are beginning to piece together Antarctica's ancient ecosystems, they still have a lot to learn about the dinosaurs that lived there.

"There are likely many more dinosaurs to be discovered on the continent," Barrett said. "As climate change causes ice to retreat we may indeed find further evidence of this past biodiversity."

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?

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!

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.

In the 1970s, paleontologist John Ostrom revived the theory that modern birds are evolved from theropod dinosaurs, a group that includes Tyrannosaurus rex. But a key piece of evidence was missing: feathered fossils. Then, a chance discovery in China upended our understanding of bird evolution.

In this excerpt from "The Story of Birds: An Evolutionary History of the Dinosaurs That Live Among Us" (Mariner Books, 2026), author and paleontologist Steve Brusatte looks at the monumental shift in dinosaur research after the first feathered dinosaur was discovered.

For well over a century, since its discovery in the Bavarian lithographic mines in 1861, the fossil bird Archaeopteryx was the oldest and most primitive creature known to have feathers. Then, in the autumn of 1996, this understanding was upended. Some revolutions start with a single shot; this one began with a chance encounter and a handful of photographs.

As the trees in Central Park dropped their leaves, paleontologists from around the world converged across the street, at the American Museum of Natural History, in mid-October for the annual meeting of the Society of Vertebrate Paleontology. A few weeks earlier, the Canadian dinosaur hunter Phil Currie had been in China, leading a group of tourists to dinosaur dig sites. While there, he spied something peculiar in the backroom of a Beijing museum, discovered by a farmer named Yumin Li two months prior. It was the skeleton of a small dinosaur, about the size of a chicken, fossilized as if frozen in time, in a muddy rock imbued with volcanic ash, a sign it was overcome by a sudden cataclysm.

Rapid burial had locked in the dainty details of the skeleton, but it was the stuff surrounding the bones that caught Currie's attention. The dinosaur's body was encircled by a halo of fluff. Thin, tufty, delicate strands ran along the dinosaur's back, from the top of its head to the tip of its tail. Some of the strands looked like they branched at their base. For all the world, the fuzz looked like the downfeathers of a bird.

But this wasn't a bird; it didn’t have wings, and obviously couldn't fly. It was a bona fide dinosaur — a small coelurosaur theropod, very similar to the German Compsognathus, which Huxley had held up in the 1860s as the type of transitional reptilian species birds might have evolved from.

Currie and his Chinese colleague Pei-ji Chen snapped photographs, which they printed out at the size of index cards and brought to the conference in New York. Once there, word spread fast; the rumors of a fluffy dinosaur billowed through the hallways and meeting rooms. Somebody tracked down John Ostrom, then in the twilight of his career, three decades after his discovery of the raptor Deinonychus had reignited the theory that birds evolved from dinosaurs. Currie and Chen handed him the photos. Ostrom looked shell-shocked. He began to cry, and almost fell to the floor. "I need to sit down," he stuttered, delirium taking hold.

Here it was, finally: a dinosaur with feathers. Just as Ostrom had predicted. Just as the doubters had demanded. The final piece of the puzzle, the strongest evidence that birds have dinosaur ancestry.

A crafty journalist from The New York Times caught wind of the excitement, and the next day, the front page of the Saturday edition blared with the headline "Feathery Fossil Hints Dinosaur-Bird Link," along-side articles about Bill Clinton's reelection campaign and a Yankees World Series preview. Above the bold print was a drawing of a small meat-eating dinosaur, running on its hind legs, small arms curled up, its tail a long seesaw for balance, its neck, back, and chest covered with bushy fuzz.

The artwork was needed, because the Chinese authorities barred publication of the photos. Before the year was out, Chinese scientists published a formal description of the fossil and gave it a name: Sinosauropteryx, the "Chinese reptilian wing," in honor of its transitional status between dinosaurs and birds.

Sinosauropteryx was the firing gun for a fossil rush, as farmers across Liaoning Province — a bucolic region of fields and rolling hills along the Chinese border with North Korea — fanned out in search of more feathered dinosaurs.

They knew the land better than anyone, and they knew museums would pay top money for such precious fossils. Soon, they were finding feather-covered dinosaurs in droves. The whole area, it turned out, had been bombarded by volcanic eruptions in the Jurassic and Cretaceous Periods, which quickly entombed entire ecosystems.

This was the key to the fine preservation: Normally soft bits like skin and feathers decay before a skeleton can harden into a fossil, but in this one remarkable place, feathers could easily fossilize. It was a dinosaurian Pompeii. As the new millennium dawned, the mounting Chinese discoveries transformed our image of dinosaurs.

One feathered dinosaur became ten, then hundreds, then thousands of skeletons, belonging to several dozen distinct species. Some, like the ostrich-size Beipiaosaurus, were adorned with simple filaments that looked like oversize versions of the bristle feathers of modern birds. Others, like the original Sinosauropteryx, had more complex feathers that resembled little paintbrushes, with many individual bristles branching from a root in an untidy tuft.

Much more extravagant were the feathers of the turkey-size Caudipteryx and dromaeosaurid "raptors" like Sinornithosaurus, which had true quill pens with a central shaft and many barbs extending off the sides to form vanes. Sometimes, these pennaceous feathers lined up along the hand and arm, making what could only be described as a wing, like in the crow-size Microraptor.

The roster of feathered dinosaurs got richer and richer. Even tyrannosaurs were in on the makeover: two early cousins of T. rex called Dilong and Yutyrannus were found coated in bristle and tufty feathers. Most of these plumose dinosaurs were theropods, members of the great group of meat-eaters on the family tree, but a few plant-eaters like Psittacosaurus, a primitive cousin of Triceratops with tiny horns on its head, had mohawks of bristles along their tails.

And most of these feathery fossils were from China, but soon they started to turn up elsewhere, like in Siberia, where a herd of hundreds of dog-size, duck-billed dinosaur cousins called Kulindadromeus were overwhelmed by their own volcano. This herbivore was resplendent with bristles on its head and body, branching downy tassels on its arms and legs, and curi-ous ribbonlike streamers on its knees — while meanwhile there were also scales on the lower legs and tail. Although Kulindadromeus was a vegetarian distantly related to theropods, its branching tufts — each formed by six or seven short filaments arising from a common anchor — look like they could be plucked from Sinosauropteryx or another meat-eater.

Initially, there was some skepticism that these wispy fossilized structures on the backs, tails, and arms of dinosaurs were true feathers. It was a legitimate question when Sinosauropteryx was first unveiled: Could its little strands and bristles have been something else, like degraded skin, or a freak by-product of decay and fossilization?

The discovery of full-on pennaceous quills — with shafts, barbs, and vanes — in species like Caudipteryx and Microraptor proved that many of these were genuine feathers. But what of those simpler filaments in other dinosaurs? We can be confident they are real. They not only look like the bristles and down feathers of birds today, but they share the same structure: They are hollow, chemical analysis shows they are formed of those rare CBP proteins, and when you look at them under powerful microscopes, you see they are full of melanosomes, the minuscule bubbles that hold pigments and give modern feathers their colors.

Still doubt it? Then gander at one of the most improbable fossils ever discovered, from Myanmar, announced in 2016. It's a tail of a juvenile theropod embedded in amber, shrouded in feathers, their details preserved in stunning 3D. Suspended in yellow resin, like a bug frozen into an ice cube, the feathers seem almost alive.

They may as well be bundles of down that slipped out of a pillow and stuck onto your sofa. They have a small central shaft, which branches into barbs, which further branch into barbules. And they are clearly observed growing from follicles in the skin. They are absolutely feathers, and fulfill every definition we use to characterize feathers in modern birds — but they are plastered to a dinosaur.

This bounty of feathered dinosaurs, fundamentally, was that final piece of evidence to verify what has now become paleontological consensus: Today's birds evolved from dinosaurs.

Excerpted from the book THE STORY OF BIRDS: A New History from Their Dinosaur Origins to the Present by Steve Brusatte. Copyright © 2026 by Stephen (Steve) Brusatte. From Mariner Books, an imprint of HarperCollins Publishers. Reprinted by permission.

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?

Researchers have uncovered an intriguing set of never-before-seen features in the skull of Archaeopteryx, an iconic dinosaur that is considered a key transitional fossil in the evolution of birds, a new study reports.

The features — which are absent in nonflying dinosaurs but are widespread in living birds — may have enabled Archaeopteryx to acquire, manipulate and process food more efficiently, the research team proposed in the study, which was published Feb. 2 in the journal The Innovation.

The newly discovered features include a tiny bone that indicates Archaeopteryx had a highly mobile tongue. The researchers also identified "weird" soft tissue traces interpreted as oral papillae — small, tooth-like projections on the roof of the mouth, Jingmai O'Connor, an associate curator of fossil reptiles at the Field Museum in Chicago and lead author of the study, told Live Science in an email. Finally, the team found "unusual" openings near the tip of Archaeopteryx's jaw that suggest a nerve-rich structure and may represent an early analogue of what is known as a bill-tip organ in modern birds.

The identification of these features in Archaeopteryx marks their earliest known appearance in the fossil record, according to the study, suggesting these characteristics evolved during or close to the emergence of avian dinosaurs — known as birds — which is thought to have occurred during the Late Jurassic period (roughly 161.5 million to 143 million years ago).

Modern birds are the only dinosaur lineage that survived the mass extinction event 66 million years ago. Archaeopteryx, which lived around 150 million years ago in what is now Germany, is among the oldest — if not the earliest — known dinosaur that can also be considered a bird under a broad definition, although it was probably not the first bird to evolve, O'Connor said.

Furthermore, Archaeopteryx is unlikely to have been a direct ancestor of modern birds, research suggests. According to O'Connor, Archaeopteryx represents the earliest known dinosaur with good evidence for active, feather-driven flight, although this was likely limited to brief, powered bursts.

The newly revealed features came to light during the preparation and examination of an Archaeopteryx specimen at the Field Museum that was first described scientifically in 2025.

Oral papillae help birds grip prey and guide food down their throats. This is the first time such features have been documented in the fossil record, the study noted. The flexible tongue, meanwhile, likely would have helped Archaeopteryx reach for food and manipulate it. Bill-tip organs in birds provide "added sensory information" that helps with a variety of oral tasks, such as rummaging around for food, O'Connor said.

The latest findings about Archaeopteryx, which indicate a change in dinosaur feeding abilities occurring around the origin of birds, raise the "interesting possibility" that the evolution of the novel features was driven by the increased energy demands associated with the emergence of powered, feather-driven flight, the authors propose.

Christian Foth, a paleontologist with the Museum für Naturkunde (Natural History Museum) in Berlin who was not involved in the study, told Live Science in an email that the paper has some "interesting findings" that should be explored further in other Archaeopteryx, early-bird and bird-like-dinosaur specimens. But he said he was not convinced by the authors' proposal for a new bill-tip organ analogue in the snout, and urged caution over the suggestion that the features evolved as adaptations to Archaeopteryx's flying behavior.

"Active flight requires energy, correct. But how many calories the animal in the end could use for flight depends more on the diet source itself and the digestion system, which we do not have any info on," Foth said. These adaptations may "ensure that a caught dragonfly did not fall out of the mouth," he added, "but not how well the diet was processed."

The fearsome Tyrannosaurus rex is perhaps the most iconic dinosaur that ever lived. Ever since the discovery of the first T. rex fossil in Hell Creek, Montana, in 1902, this gigantic predator — with its terrifying teeth and strangely tiny arms — has fascinated people of all ages, and played a starring role in books and films, including the Jurassic Park movies, as well as taking pride of place in museums around the world.

Yet, our picture of how this dinosaur looked and lived has changed markedly thanks to more than a century of scientific discoveries. Think you know everything there is to know about the king of the dinosaurs? Well, start the quiz below to find out if your knowledge is dino-mite or a faded fossil.

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button!

Editor's note: This article was updated on Jan. 8 at 5:00 a.m. ET to correct a conversion in a question answer.

More science quizzes

• Crocodile quiz: Test your knowledge on the prehistoric predators
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Scientists have discovered an enormous species of duck-billed dinosaur that lived in what is now New Mexico about 75 million years ago.

The dinosaur, Ahshislesaurus wimani, likely had a flat head and a bony crest low on its snout, researchers revealed in a study. The findings, which is due to be published in the Bulletin of the New Mexico Museum of Natural History and Science, suggest that duck-billed dinosaurs, or hadrosaurids, were more diverse and overlapping during the last 20 million years of the Cretaceous period (145 million to 66 million years ago) than previously thought.

Hadrosaurids were large, plant-eating dinosaurs that lived during the last 24 million years of the Cretaceous. They have "sometimes been colorfully called 'the cows of the Cretaceous,'" study co-author Steven Jasinski, a paleontologist at the Harrisburg University of Science and Technology in Pennsylvania, said in a statement. "While this may not be a perfect metaphor, they likely were living in herds and would have been conspicuously present in the environments of northern New Mexico near the end of the Cretaceous."

According to the statement, A. wimani could potentially have grown up to 40 feet (12 meters) long.

One set of A. wimani fossils discovered in 1916 were previously identified as a member of the hadrosaurid genus Kritosaurus. But existing fossil specimens are frequently being reevaluated as more data and fossils become available.

In the new study, the researchers revisited that set of fossils — including an incomplete skull, lower jawbone, and several vertebrae — from the Kirtland Formation in New Mexico. The fossils were housed at the Smithsonian National Museum of Natural History.

"As a general rule … skulls are really the basis for identifying differences in animals," study co-author Anthony Fiorillo, the executive director of the New Mexico Museum of Natural History and Science, said in a separate statement. "When you have a skull and you're noticing differences, that carries more weight than, say, you found a toe bone that looks different from that toe bone."

By comparing the skull to those of other hadrosaurids, the team found that its shape and features were distinct enough from other hadrosaurid skulls to suggest it was likely a different species. A. wimani is closely related to Kritosaurus, suggesting that their evolutionary lines had split not long before.

"Kritosaurus is still a valid genus with species of its own," study co-author Edward Malinzak, a paleontologist at Penn State University Lehigh Valley, said in the second statement. "We took a specimen that was lumped in as an individual of Kritosaurus and determined it had significantly distinct anatomical features to warrant being its own genus and species."

It's not clear yet how the related species co-existed in the same environment, the researchers wrote in the study. But tracing the history and extent of different species could help scientists understand the environment they lived in, as well as the evolutionary history of duck-billed dinosaurs.

"The lineages appear to have co-existed in the region for a time," Malinzak said. "It showed that this group not only exploded with diversity across the continent at one point, but also contributed to the world-wide spread of this group in the Late Cretaceous."

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 discovered a record-breaking number of fossilized dinosaur footprints and swim tracks in a national park in central Bolivia.

The tracksite sits along what was once an ancient coastline, with ripple marks extending alongside the footprints and other imprints in a northwest-southeast direction, according to a new study. Most of the tracks belong to bipedal, three-toed dinosaurs known as theropods that lived at the end of the Cretaceous period (145 million to 66 million years ago), but many bird tracks are also preserved, the scientists noted in the paper, which was published Wednesday (Dec. 3) in the journal PLOS One.

"This is the highest number of dinosaur footprints ever found for a single tracksite thus far," study co-author Jeremy McLarty, a paleontologist and associate professor at the Southwestern Adventist University in Texas, told Live Science in an email. "In addition to preserving the most dinosaur tracks worldwide, it also preserves the highest number of swim trackways in the world."

In total, McLarty and his colleagues counted 16,600 theropod footprints and 1,378 swim tracks. These were found in Bolivia's Carreras Pampa tracksite, which was already known but hadn't been properly studied or documented.

Carreras Pampa extends across 80,570 square feet (7,485 square meters) in Torotoro National Park. The initial work involved sweeping debris off the dinosaur imprints with brooms, clearing the tracksite of rocks and removing sediment in places where additional tracks were likely to be found.

The team discovered a huge variety of footprint shapes and sizes, indicating that many types of theropod dinosaurs roamed along the ancient coastline. Several tracks had footprints shorter than 4 inches (10 centimeters), which is rare in the fossil record, according to the study. It's unclear if these footprints were made by small theropod species such as Coelophysis or by juveniles of larger species, the researchers wrote.

The largest footprints were more than 12 inches (30 cm) long, and the team thinks these may have been made by mid-size theropod dinosaurs such as Dilophosaurus or Allosaurus. Large theropods such as Tyrannosaurus rex and Giganotosaurus typically leave 16-inch-long (40 cm) footprints, the researchers noted.

Carreras Pampa is unique because the footprints show different dinosaur behaviors, such as walking, running, swimming, tail-dragging and making sharp turns. "It preserves evidence of several types of unusually preserved locomotive behaviors, and preserves one of the highest numbers of dinosaur tail traces anywhere in the world," McLarty said.

The swim tracks are straight or comma-shaped grooves that often have one or two similar but smaller grooves next to them, McLarty said. The main groove is from theropods scratching the sediment at the bottom of the water with their middle toe, while the smaller grooves are from the other toes. Unlike other sites that preserve only individual dinosaur swim tracks, Carreras Pampa preserves alternating left and right tracks, he said.

The abundance of imprints shows that Carreras Pampa was a prehistoric highway, and the parallel orientation of some trackways suggests some dinosaurs traveled in groups.

Bolivia is known for being a dino track hotspot.

"The tracksite with the next highest number of tracks is also in Bolivia," McLarty said. "The Cal Orck'o tracksite is located in an active quarry as a nearly vertical wall and is long and thin. The Carreras Pampa tracksite is spread out across a wider area."

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.

Two extremely rare dinosaur "mummies" found in the badlands of Wyoming are the first examples of hoofed reptiles, according to a new study.

Researchers discovered the pair of 66 million-year-old duck-billed dinosaur (Edmontosaurus annectens) skeletons complete with skin, spikes and hooves, as if the creatures had been naturally mummified.

The fossils aren't true mummies, as their original tissues have been replaced with rock, but they give scientists an unprecedented look at duck-billed dinosaur biology, confirming they had hooves. The researchers reported their findings Oct. 23 in the journal Science.

"It's the first time we’ve had a complete, fleshed-out view of a large dinosaur that we can really feel confident about," study senior author Paul Sereno, a professor of organismal biology and anatomy at the University of Chicago, said in a statement.

Duck-billed dinosaurs used their hooves to stomp through mud at the end of the Cretaceous period (145 million to 66 million years ago). They lived alongside other large dinosaurs, such as Tyrannosaurus rex and Triceratops, just before the age of dinosaurs came to a crashing end when a massive asteroid hit Earth and wiped them all out (except for birds).

Dinosaur mummies are exceptionally preserved fossils that contain a clay copy of dinosaur skin and other organic tissues. Several of these fossils were discovered in Wyoming in the early 1900s, which inspired the new research. Sereno and his colleagues found the two new specimens by tracking down the locations of the historical discoveries, using old photographs and letters, and mapping out what they described as a "mummy zone."

One of the newly discovered Edmontosaurus specimens, nicknamed "Ed Jr.," was a late juvenile and estimated to be about 2 years old at the time of its death. The other specimen, nicknamed "Ed Sr.," was an early adult about 5 to 8 years old when it perished.

The researchers reconstructed the dinosaurs' biology, movement and preservation using a variety of imaging techniques, including X-rays and micro-CT scans, as well as by analyzing clay, examining the site where they were discovered, and studying fossilized duck-billed dinosaur footprints.

The dinosaurs had a fleshy crest running along their neck and trunk that transitioned into a row of spikes at the tail. Small, pebble-like scales also peppered the animal's lower body and tail, the largest of which were only 0.2 inches (4 millimeters) across — tiny considering the dinosaur could grow to more than 40 feet (12 meters) long, according to the statement.

The team determined that the mummification-like preservation occurred because the dinosaurs' bodies were dried out in the sun — they may well have perished in a drought — before being quickly covered in a flash flood. Static electricity, reacting with microorganisms on the surface of the carcasses, then sucked clay from the wet sediment to form a thin template later around the remains. The organic material then slowly decayed and was replaced with rock.

"There are so many amazing 'firsts' preserved in these duck-billed mummies — the earliest hooves documented in a land vertebrate, the first confirmed hooved reptile, and the first hooved four-legged animal with different forelimb and hindlimb posture," Sereno said.

Some of the last dinosaurs in the world were healthy and thriving right up until the day they were annihilated by asteroid Armageddon, a new study on fossils from New Mexico finds.

Scientists have debated for decades whether non-avian dinosaurs were in decline before a massive asteroid struck Mexico's Yucatán Peninsula at the end of the Cretaceous period (145 million to 66 million years ago). The new study, published Thursday (Oct. 23) in the journal Science, supports previous evidence that the dinosaurs were struck down in their prime and might have still roamed Earth if it weren't for that pesky asteroid.

Researchers dated rocks from the Naashoibito Member fossil site in New Mexico, which preserved a rich Cretaceous ecosystem home to a variety of dinosaurs, including the 70-foot-long (21 meters) long-necked sauropod known as Alamosaurus, as well as meat-eating tyrannosaurs, horned dinosaurs and duck-billed dinosaurs. The dating revealed that this ecosystem existed just before the Chicxulub asteroid strike, suggesting that New Mexico's last dinosaurs were doing well before the giant space rock brought death from the sky.

"At least before the mass extinction event, they appear to be thriving," study lead author Andrew Flynn, an assistant professor in the Department of Geological Sciences at New Mexico State University, told Live Science in an email. "There is a diverse dinosaur fauna in the Nasshoibito Member in New Mexico so the dinosaur population appears to be healthy."

The asteroid triggered a mass extinction event in which around 75% of living species went extinct, including all dinosaurs, except for birds. Previously, some research has suggested that dinosaur diversity declined as part of a restructuring in the Maastrichtian age (72.1 million to 66 million years ago) of the Cretaceous, with environmental factors such as climate change making the dinosaurs more vulnerable to catastrophe. However, other researchers have argued that the asteroid interrupted an age of prosperity for the dinosaurs.

Much of what scientists know about the Cretaceous-Paleogene (K-Pg) boundary — the rocks that mark the end of the Cretaceous period — has come from formations such as Hell Creek and Fort Union in the northern Great Plains U.S., which means there's a lot of uncertainty surrounding what was happening elsewhere.

Paleontologists knew that the Naashoibito Member featured New Mexico's last known non-avian dinosaurs, but the precise age of these fossils has been up for debate. In the new study, researchers sought to resolve this uncertainty by combining two rock dating methods.

"We wanted to get two different, independent ways of determining the age of the rocks," Flynn said.

The first of these methods involved measuring radioactive decay in argon isotopes. The second took advantage of magnetic fields: Earth's magnetic field flips between a "normal" state, when magnetic north is north (how it is today), and a reversed state, when magnetic north is south. Researchers know when these flips have occurred through Earth's history, so by measuring magnetic pole direction in rocks, they can deduce their age.

The dating methods placed the Naashoibito Member between about 66.4 million and 66 million years ago — meaning that the dinosaurs there lived within about 340,000 years of the asteroid strike. The researchers also found that New Mexico's dinosaurs were unique, suggesting that western North America had distinct pockets of dinosaur diversity.

"These revised estimates of dinosaur diversity during the Maastrichtian still do not match the bounty of the preceding Campanian Age — the apparent zenith of dinosaur diversification in North America," Lindsay Zanno, a paleontologist at North Carolina State University who was not involved in the study wrote in an accompanying perspective published in Science. "Nonetheless, current estimates of Maastrichtian biodiversity are still higher than those for most other Late Cretaceous ages."

The new study paints a picture of dinosaurs suffering an abrupt extinction with the asteroid strike, leading to the rapid rise of mammals soon after. However, it's still unclear whether this was the case everywhere.

"This work really highlights the need to work on new, previously understudied localities across this incredibly important time in Earth's history," Flynn said. "Just adding one new, well dated dinosaur bearing locality in western North America allows us to see this really interesting picture of dinosaurs."

Scientists have been using ancient DNA to investigate questions about extinct animals since 1984, when researchers recovered two pieces of DNA from a museum specimen of a quagga, a zebra-like species that went extinct in the 19th century. Over the past 40 years, advancements in technology have allowed scientists to sequence older and older DNA from animals and plants, with the current record held by a 2.4 million-year-old Greenland ecosystem.

But could DNA potentially last even longer? Because DNA preservation depends on a huge number of environmental factors, scientists are still grappling with the question of how long DNA can theoretically and realistically last.

"It's less than people thought in the early '90s but more than people thought in the early 2000s," Tom Gilbert, director of the Danish National Research Foundation Center for Evolutionary Hologenomics, told Live Science. "The reason I say that is the early '90s were very much the 'Jurassic Park' era."

Michael Crichton's sci-fi novel "Jurassic Park" (Knopf, 1990) — in which a billionaire founder of a bioengineering firm extracts dinosaur DNA from insects fossilized in amber and resurrects several extinct species — was an entry point into the world of ancient DNA for a generation of people, including scientists.

"People started looking for DNA in Cretaceous fossils" of organisms that lived 145 million to 66 million years ago, Gilbert said, "and the DNA turned out to be things like bacteria that weren't that old."

Gilbert co-authored a 2012 study that used statistics to model the "half-life" of DNA in bone and to check claims of the extraordinary survival of DNA in Cretaceous period specimens.

The team analyzed the mitochondrial DNA in 158 bones from extinct New Zealand moa birds that had been carbon-dated. By looking at how the DNA broke down over time, the team discovered that DNA's "half-life" — when half of the DNA bonds in a sample would be broken — is about 521 years.

This model predicted that, under ideal conditions, DNA could survive for about 6.8 million years — not nearly long enough for Jurassic Park to become a reality.

"The best conditions for ancient DNA preservation are cold, dark, dry and recent," Jennifer Raff, a biological anthropologist at the University of Kansas, told Live Science. "These permafrost conditions are where you can get the best DNA usually."

This explains why the oldest DNA to date has been found in 2.4 million-year-old sediments in Greenland and why the oldest genome sequenced to date — from a mammoth that lived 1.2 million years ago — was found in Siberia.

This raises the question of what's the oldest DNA from a human or close human relative. Humans evolved largely in geographic areas that are hot and damp, where DNA preservation is poor. This limits how much we can learn about our distant ancestors and related species from their DNA.

DNA from Neanderthals, our closest extinct human cousin, was extracted in 1997 from a 40,000-year-old Neanderthal discovered in 1856 in the Kleine Feldhofer cave in Germany. Meanwhile, the world's oldest DNA from a human relative comes from Sima de los Huesos ("Pit of Bones") in an underground cave in the Atapuerca Mountains of Spain. In 2022, researchers sequenced DNA from a thigh bone of a human relative that lived 400,000 years ago, suggesting that the group may have given rise to both Neanderthals and Denisovans.

Ancient DNA evidence from Africa, where humans evolved over millions of years, is currently sparse. Due to natural preservation issues, the oldest DNA from sub-Saharan Africa is only 20,000 years old and from modern Homo sapiens. Together with DNA's predicted half-life, this means scientists are limited in investigating the genetics of our earliest ancestors.

Recent advances in paleoproteomics — the study of ancient proteins — are beginning to provide small amounts of genetic information from human relatives that lived 3.5 million years ago. But getting DNA from relatives like the australopithecines, a group that includes Lucy, is next to nil.

"I don't think we'll be able to get DNA from australopithecines," which lived around 4.5 million to 1.2 million years ago, Raff said, "because those are all in Africa and the conditions are not ideal." But it still may be possible to extract DNA from more recent hominins, a group that encompasses our close human ancestors and relatives.

"I'm much more optimistic about Homo erectus," Raff said. "You've got Homo erectus in places where you could conceivably have good DNA preservation," including the Republic of Georgia and China.

Even if experts find a place with ideal conditions for ancient DNA preservation — cold, dark and dry — there's one final parameter that's important to consider, Gilbert said: whether the surviving DNA is meaningful.

"There's a minimum length of DNA sequence you need that you can uniquely identify," Gilbert said. "If you take a book and cut it up into chapters, you can identify the book. If you cut it up into words, it's much harder. Cut it up into letters, it's impossible."

Although 2.4 million years is the current record for the oldest meaningful DNA to be sequenced, Gilbert said, older DNA may be found in the future, perhaps under Antarctic ice sheets.

"To be honest, had I been asked in 2003 how long DNA could last, the absolute wisdom of all the people in the know would have been 100,000 years," Gilbert said. "So we're off by a factor of 20 already."

Evolution quiz: Can you naturally select the correct answers?

There is a new dinosaur king of South America. This newly discovered top predator, named Joaquinraptor casali, was some 23 feet (7 metres) long and was a fast-moving hunter with powerful "claws like hedge trimmers."

And the massive beast's remains were found with the leg bone of an ancient crocodile relative locked in its jaws.

Lead author Lucio Ibiricu, a paleontologist at CONICET's Patagonian Institute of Geology and Paleontology in Chubut, Argentina, and his colleagues unearthed the well-preserved fossil — including much of the skull, ribs, vertebrae and fore and hind-limbs — from the Lago Colhué Huapi Formation of south-central Chubut Province in central Patagonia, Argentina.

J. casali was a type of theropod dinosaur known as a megaraptor, or "large thief," that lived in the final stages of the Cretaceous period between about 70 million and 66 million years ago, before the Chicxulub asteroid slammed into the Yucatán Peninsula causing the Cretaceous–Paleogene extinction event that spelled the end for dinosaurs (except for some birds).

The megaraptors, which lived across South America, Asia and Australia, were carnivores with elongated skulls, powerful arms and big claws.

Related: Oldest-known dome-headed dinosaur discovered sticking out of a cliff in Mongolia's Gobi Desert

"Joaquinraptor provides a clearer understanding of how this enigmatic group of predatory dinosaurs lived and evolved," Darla Zelenitsky, a paleontologist at the University of Calgary in Canada who wasn't involved in the work, told Live Science. "Deemed the latest surviving megaraptoran, this fossil provides insight into the final phase of their evolutionary history in South America prior to the mass extinction."

The discovery reveals that megaraptorans (any dinosaur belonging to the Megaraptora clade, which includes megaraptors) stayed relatively large until the end of the Cretaceous, likely filling the apex predator niche in the region of southern Patagonia at that time, she said.

The lands where Joaquinraptor roamed were very different from the cool, dry Patagonian climate of today, though. Sediment from the same layer as the fossil find reveals that it was probably a warm, humid floodplain near the sea.

Ibiricu told Live Science that the first hints of the fossil were uncovered in 2019, but it took three field seasons to fully unearth it. When they finally excavated the fossil, the researchers discovered the leg bone of a crocodile relative in Joaquinraptor's jaws, hinting at its diet and that it was likely the top predator in the area.

The researchers then analyzed the histology, or microstructure, of a tibia and rib bone to work out how old the specimen was when it died.

"We know based on histology that this was a sexually mature individual but it might have been able to grow a little bit more. We know that when it died, it was at least 19 years old," Ibiricu said.

Bone measurements also led the researchers to estimate that Joaquinraptor would have been about 23 feet long and weighed more than 2,200 pounds (1,000 kilograms). The find is described in a paper published Tuesday (Sept. 23) in the journal Nature Communications.

"This is a fantastic discovery and one of the most intriguing new dinosaur discoveries in recent memory," Steve Brusatte, a paleontologist at the University of Edinburgh, Scotland who wasn't involved in the study, told Live Science. "It was dinosaurs like these that topped the southern food chain at the same time that Tyrannosaurus rex was reigning supreme in North America."

Brusatte said the two predators were drastically different, though. "Joaquinraptor was slender and svelte and fast, and it had ridiculously oversized arms and claws, like hedge trimmers. Its arms and hands make T. rex look puny by comparison, Arnold Schwarzenegger vs Danny DeVito, at least in the arms category," he said.

These differences would have meant the two apex predators would have hunted very distinctly, Zelenitsky said. "At more than four times the weight of Joaquinraptor, T. rex was a brute force predator — massive, with a bone-crushing bite. But Joaquinraptor was swift, slender and attacked with surgical precision. It would have delivered slashing bites and had long arms with big claws for grabbing, slashing and manipulating prey," she said.

Around 66 million years ago, the reign of the dinosaurs came to a fiery end. An asteroid about 7 miles (12 kilometers) wide, flying at 27,000 mph (43,000 km/h), slammed directly into Earth. The impact triggered a cascade of deadly events that led to the fifth mass extinction that eliminated dinosaurs, with the exception of some birds.

But what happened to the Mount Everest-size asteroid?

When it smashed into Earth "with the energy of about 8 billion times a World War II-era nuclear bomb, the asteroid basically vaporizes," Sean Gulick, research professor and co-director of the Center for Planetary Systems Habitability at the University of Texas at Austin, told Live Science. The asteroid became "a fine dust that ends up in the upper atmosphere and rains down" over the entire planet.

Decades of asteroid dust rained down to form what is now known as the iridium anomaly, a thin layer of rock that has 80 times more iridium than anywhere else in Earth's crust, Gulick said. While iridium is highly concentrated in asteroids, it's almost nonexistent in Earth's outer shell — a key piece of evidence linking the 66 million-year-old layer to the dinosaur-killing asteroid.

Perhaps the only chunk of the asteroid known to exist is a sesame-seed-size fragment found by Frank Kyte, a geochemist at UCLA. The rock bit was discovered in a core sample drilled off Hawaii, Kyte reported in the journal Nature in 1998. More tiny shards were allegedly discovered in 2022, but that claim was not backed by peer review.

"We would have to get pretty lucky to find a larger chunk," Gulick said. But if we did, scientists could learn more about the "process of shock" experienced by the asteroid itself and make even more precise estimates about the pressures and temperatures it experienced, for example.

The asteroid left behind a number of additional clues about its journey, including the huge crater it created when the giant rock collided with Earth. Roughly 110 miles (180 km) wide and about 12 miles (20 km) deep, the Chicxulub crater in what is now Mexico bears the massive scar of the asteroid. Named after a town near the center of the impact, the crater has been covered by rock and sediment that shifted over tens of millions of years and a major portion is hidden under the Gulf of Mexico. But still visible from the surface is an arc of sinkholes along part of its rim that formed in weakened limestone.

Related: What if a giant asteroid had not wiped out the dinosaurs?

The impact also generated a nearly mile-high tsunami that moved through the entire ocean, moving water as fast as 89 mph (143 km/h). The massive waves caused marks on the seafloor — called "megaripples" — that were as tall as five-story buildings and are preserved deep beneath Louisiana. A seismic survey revealed that the water that formed the ripples came from the direction of the Chicxulub crater.

Besides killing the unlucky creatures in the immediate area of the asteroid's landfall and subsequent tsunami, the impact triggered a series of other devastating effects, including deadly acid rain and a global firestorm. But perhaps most destructive was the massive cloud of debris that shrouded Earth, drastically cooling the planet, blocking sunlight and photosynthesis, and collapsing the food chain (although the length of this "nuclear winter" is debated). The asteroid and its aftermath are widely agreed to be the cause of the nonavian dinosaurs' extinction and ultimately wiped out about 75% of species on Earth.

"The energy release was like fighting total nuclear war, over and over again, 10,000 times," said Alan Hildebrand, a planetary scientist and associate professor at the University of Calgary. Hildebrand co-authored the paper that published the discovery of the Chicxulub crater in 1991, and that work provided major evidence linking the crater's connection to the death of the dinosaurs.

It's no surprise to Hildebrand that the asteroid wiped out the majority of life on Earth.

In Alberta, where he was during the time of the interview, Hildebrand marveled at the sheer power of the impact. The nearby layer from the Chicxilub impact is 0.4 to 0.8 inches (1 to 2 cm) thick, "and that material was blasted up here from the Yucatán Peninsula," he said.

What's inside Earth quiz: Test your knowledge of our planet's hidden layers

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."

A gigantic crocodile-like hypercarnivore likely hunted dinosaurs 70 million years ago in what is now Argentina, a new study reveals.

Researchers discovered the fossilized skeleton from the extinct apex predator in southern Patagonia in 2020. It grew up to around 11.5 feet (3.5 meters) long and weighed about 550 pounds (250 kilograms).

The creature is named Kostensuchus atrox after the Patagonian wind called "the Kosten" and the Egyptian crocodile-headed god Sobek, also known as Suchus. K. atrox was hypercarnivorous, meaning more than 70% of its diet was meat. Equipped with a broad snout, big teeth and robust forelimbs, K. atrox's anatomy suggests it was capable of taking down large prey in South America's Cretaceous (145 million to 66 million years ago) ecosystem, according to a new study published Wednesday (Aug. 27) in the journal PLOS One.

The discovery highlights the fact that dinosaurs lived in the company of a wide diversity of organisms, said study lead author Fernando Novas, a paleontologist at the National Scientific and Technical Research Council (CONICET) and the Félix de Azara Natural History Foundation in Argentina.

"In particular, terrestrial crocodylians were notably diverse and abundant during Cretaceous times in South America and Africa, including small and large, meat-eating and plant-eating forms, revealing that these continents were 'land of crocs,'" Novas told Live Science in an email. "These extinct crocodyles competed and preyed upon dinosaurs, and played an important role in the structure of vanished ecosystems."

Related: Bite marks reveal giant terror birds were potentially prey for another apex predator — humongous caiman

K. atrox was part of a group of reptiles called peirosaurid crocodyliforms, which are extinct relatives of living crocodiles. The newly discovered fossils were so well preserved that K. atrox is one of the best peirosaurid crocodyliform examples ever found, and is the most complete large and broad-snouted member on record, according to the study.

Researchers discovered K. atrox in Patagonia's Chorrillo rock formation. They also discovered a larger carnivorous dinosaur named Maip macrothorax around the same time, which was unveiled in 2022. M. macrothorax was a megaraptor that stood at around 30 to 33 feet (9 to 10 m) long, CBBC Newsround reported in 2022.

While K. atrox was smaller than M. macrothorax, Novas said it was capable of preying upon small to medium-size dinosaurs, meaning it rivaled the top dinosaur predators in the region.

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.

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.

Around 100 million years ago, male dinosaurs entered a "mating arena" in Colorado and danced their hearts out to attract females, a new study suggests.

Researchers uncovered a series of mating display scrapes preserved on the surface of rocks at Dinosaur Ridge in Jefferson County, Colorado. The state is known for dinosaur track sites, with previous studies suggesting that dinosaurs returned to these mating spots over successive breeding seasons.

The latest marks identified at Dinosaur Ridge suggest that multiple individuals participated in mating display behavior there during the Cretaceous period (145 million to 66 million years ago) and allow the ridge to be classed as a "display arena," or lek, according to the new study, published online on June 4 in the journal Cretaceous Research.

The scapes were left by theropods, a group of bipedal dinosaurs that included Tyrannosaurus rex. Study lead author Caldwell Buntin, a lecturer in Earth science at Old Dominion University in Virginia, told Live Science that they don't have any direct evidence of what species left the marks, but it was a small therapod, around the size of a modern-day ostrich.

Researchers believe that the dinosaurs showed off to potential mates by jabbing their claws deep into the sand, dragging their feet and kicking up sand behind them. Buntin noted that the animals would alternate between their two feet when kicking up sand and had different moves.

"We can tell they had two moves so far, one walking backwards and one moving side to side," Buntin said in an email. "If they were really excited they would step a few feet backwards and repeat the motion, which usually erases the back half of each earlier set of scrapes. When this happened 3 or more times a few of these show a counter-clockwise turn, kind of like the moonwalk with a little spin."

Related: Mysterious 'runner' dinosaur a sign there are more Jurassic secrets to unlock beneath western US

"When moving side-to-side, they would take a step or two to the side, face the same direction, and repeat their scrape movements," Buntin said. "This is usually recorded by two sets of scrapes right next to one another, or one and a half sets of scrapes if they only took a half step over."

Lekking is a common behavior among modern birds. For example, male greater sage-grouse (Centrocercus urophasianus) perform an elaborate sunrise display each spring, inflating air sacks on their chests and generally strutting their stuff for the attention of females.

The lek at Dinosaur Ridge dates back to the Cretaceous period's Cenomanian age (100.5 million to 93.9 million years ago). Buntin and his colleagues used drones to capture high-resolution images of the site and identified a total of 25 new scrapes on two surfaces at the ridge.

"It was very exciting to see the new scrapes in the imagery when we processed it!" Buntin said. "Originally only 2 or 3 of the new traces were immediately evident, but within an hour or so we had noticed almost a dozen new of the scrapes. It was quite surreal."

Researchers have unearthed the oldest pterosaur ever discovered in North America and named it the "ash-winged dawn goddess."

The 209 million-year-old pterosaur was among a cache of more than 1,000 Triassic fossils extracted from rocks in the Petrified Forest National Park in Arizona. Eotephradactylus mcintireae is partly named after volcanic ash found in the fossil bed and Eos, the Greek goddess of the dawn, because it evolved near the beginning, or dawn, of pterosaurs' evolutionary history.

Pterosaurs, informally called "pterodactyls," were flying reptiles that dominated the skies during the age of dinosaurs. The group produced many giants, some with wingspans stretching to around 36 feet (11 meters), but E. mcintireae and the other early members were tiny by comparison.

"This pterosaur would be the size of a small seagull, and could have sat on your shoulder," study lead author Ben Kligman, a paleontologist at the Smithsonian's National Museum of Natural History in Washington, D.C., told Live Science in an email.

E. mcintireae was just one member of a lost ecosystem described in the study, published Monday (July 7) in the journal PNAS. The cache of Arizona fossils also included giant amphibians, freshwater sharks, armored crocodile-like creatures and one of the oldest known turtle fossils.

These finds help researchers understand what animals were alive before the violent mass extinction event, likely triggered by volcanic eruptions, that brought the Triassic period to a close around 201 million years ago.

Related: Giant pterosaurs weren't only good at flying, they could walk among dinosaurs too

Towards the end of the Triassic, northeastern Arizona was located just above the equator in the middle of the supercontinent Pangaea. At the time, the semi-arid landscape was marked with small rivers and channels that were likely prone to flooding, according to a statement released by the Smithsonian. Researchers suspect that a flood washed over the tiny pterosaur and other animals living in the region at the time, burying their bodies in sediment and ash.

A team of scientists first discovered what remained of the Triassic bonebed in 2011. The fossils were mostly small and delicate, so rather than trying to excavate them in the field, the team extracted large chunks of sediment and worked through them in labs. Many chunks went to the Smithsonian National Museum of Natural History, where volunteers spent thousands of hours carefully extracting the fossils. A volunteer named Suzanne McIntire extracted a jaw belonging to the pterosaur in 2013 — the species name mcintireae honors her discovery.

Kligman began working on the fossils in 2018, after the jaw had been discovered, and said he doubted the fossil was a pterosaur at first — at the time, researchers had only found one early pterosaur in North America, and none had ever been found in sediment deposited in a river.

"When I finally examined the jaw my doubts were put to rest — the distinctive teeth and jaw anatomy was unmistakably from a pterosaur," Kligman said. "I was most surprised by the fact that a delicate, tiny jaw like this one had not been destroyed by the movement of river gravel prior to it being fossilized, suggesting that the bonebed was preserving a unique fossilization setting."

The bonebed revealed a community of evolutionary newcomers, such as pterosaurs and turtles, sharing the landscape with each other and more ancient animals, such as giant amphibians, before the latter went extinct at the end of the Triassic.

"The presence of the pterosaur Eotephradactylus living and interacting in a community alongside groups like frogs, lizard relatives, and turtles is the first occurrence of this community type in the fossil record — these groups are commonly found living together in post-Triassic communities from the Jurassic and Cretaceous, however they had never been found together preceding the end-Triassic extinction event 201 million years ago," Kligman said.

Dinosaurs are hitting movie theaters this summer with "Jurassic World Rebirth" debuting on Wednesday (July 2). The series that started more than 30 years ago with "Jurassic Park" is still one of the only major live action blockbuster franchises that has propelled dinosaurs to the big screen. So, what's it like being a paleontologist who advises Hollywood on these Mesozoic creatures?

Steve Brusatte, a vertebrate palaeontologist and evolutionary biologist at the University of Edinburgh in Scotland, is the scientific advisor to the "Jurassic World" movies, including the latest, which stars Scarlett Johansson, Mahershala Ali and Jonathan Bailey. Live Science emailed Brusatte several questions to get to the meat of the matter: What's his favorite scene from "Jurassic World Rebirth," what's an inaccuracy from the "Jurassic Park" films he'd like to correct, and, most importantly, if a dinosaur were to attack, which one would he prefer?

Hannah Osborne: How different would the first films be now knowing what we know about dinosaurs today?

Steve Brusatte: The first Jurassic Park came out in 1993, and in the more than 30 years since, we've learned a tremendous amount about dinosaurs. There have been something like 1,000 or more new dinosaur species discovered since then. CT scanning and molecular sampling of fossils have revolutionized our understanding of how dinosaurs grew, moved, reproduced, hunted and socialized. And we now know that a lot of dinosaurs had feathers. But still, even with all of that, the image of dinosaurs in the original film is not too far removed from what we know today. Those dinosaurs still feel realistic in their postures and behaviors. They still look good on the screen. The film has aged well!

But of course, we can incorporate the newer scientific discoveries into the new films.

HO: If you could go back in time to study one period of the Mesozoic in person, which would it be?

SB: Although T. rex will always be my favorite dinosaur, and it lived right at the end of the Age of Dinosaurs, in the closing moments of the Cretaceous period 66 million years ago, my choice would be another period entirely: The Triassic. The time spanning between about 252 [million] and 201 million years ago, bookended by two of the worst mass extinctions in Earth's history, each caused by apocalyptic volcanic eruptions.

This was the time of the supercontinent Pangaea, when all of the world's land was gathered together. And on this supercontinent the very first dinosaurs took their very first steps. These pioneering dinosaurs looked nothing like T. rex or Brontosaurus. They were merely the size of cats or dogs. But they were smart, and ran fast, and lived active and energetic lifestyles. How glorious it would have been to see them — the forebears of the dinosaur dynasty to come.

HO: What's the biggest inaccuracy from past Jurassic Park films you'd like to set the record straight on?

SB: It has to be the feathers. The original Jurassic Park rampaged with all sorts of green scaly dinosaurs, which looked like overgrown lizards or crocodiles. That was in line with what we knew about dinosaurs at the time, in 1993. But then, three years later, in China, a farmer out working his fields stumbled upon a gorgeously preserved dinosaur skeleton embedded in rock. Petrified feathers surrounded the bones. This was the first of many discoveries of similar dinosaurs, rapidly buried by volcanic eruptions, covered in feathery fluff.

We now know that many dinosaurs were fuzzy, and some, like the real Velociraptor, even had wings on its arms. In an alternative history, those first feathered dinosaurs would have been found a few years earlier, and Steven Spielberg could have put some feathers on his Velociraptors.

Related: Jurassic Park movies ranked, worst to best

HO: How does the science advisor process work? Does the studio come up with ideas and then you say yes/no, or vice versa? At what point do you get involved?

SB: My job is advisory. I am always on call, whenever the director, or artists or writers have any questions about dinosaurs. I see myself as an advocate for the science, and my mission is to make sure that the science behind dinosaurs is always there, in the ears of the creative geniuses who are writing and making the films. Most of my work happens early on, when the script is being ironed out and the designs for the dinosaur characters are being developed. It entails a lot of Zoom chats, phone calls and emails. A lot of talking, really.

Me giving feedback on ideas, whether it is a plot line, or more usually, the design of a dinosaur. It's not my job to approve or veto anything, but just to give my opinion. And I know that opinion will be weighed against many other things as the film takes shape.

HO: How do you balance entertainment with scientific accuracy?

SB: Ultimately these films are summer Hollywood monster movie blockbusters. They are not nature documentaries. They are meant to entertain. And more than anything, I am impressed and thankful that the Jurassic Park and Jurassic World series has always had paleontology advisors, for all seven films. They don't need to do this. I don't think most sci-fi films in outer space have astrophysics consultants. But the Jurassic franchise has always valued real dinosaurs.

Of course, scientific accuracy is just one component to making a dinosaur character memorable on screen. The character has to be recognizable, it has to have personality, it has to carry a story line, and it has to be dramatic. The same way that biopics of famous humans might exaggerate their features or personalities for dramatic effect, the Jurassic dinosaurs might not hew exactly to scientific precision. And I am OK with that. Because after all, we are talking about extinct species that lived millions of years ago. Nobody has seen these dinosaurs alive. There is so much we don't know about how they looked and behaved. So we always need some artistic license when it comes to imagining them.

HO: How do you become a science advisor on a big movie like this?

SB: By a stroke of incredible luck and good fortune. It's not like there is an application process. Instead, the timing just worked out. The eminent paleontologist Jack Horner served as consultant for the first five films, but then he retired. When Colin Trevorrow, the director of two of the Jurassic World films, was starting to develop Dominion in 2018, he had read a book I had recently written (The Rise and Fall of the Dinosaurs). He reached out, and I obviously thought his email was a joke — a trick being played by one of my colleagues or students. But we connected and it turned out to actually be Colin, and then we met up in Edinburgh where I live, and had a great chat, and he offered me the position. And then I was thrilled to return for Rebirth, as Colin handed the reins over to Gareth Edwards to direct the latest installment.

HO: To have a fresh supply of villains, the Jurassic World franchise keeps inventing new dinosaurs that are scarier than T. rex. Do you think there are any real-life dinosaurs that are actually scarier than T. rex?

Short answer, no. I think T. rex was the ultimate dinosaur. It was a bus-sized monster, with a head the size of a bathtub, with over 50 railroad spike teeth that could crush the bones of its prey. And it was smart, with a big brain for a dinosaur, and keen senses of smell and hearing and vision. It doesn't get any badder than that.

SB: What's your favorite dinosaur in the new movie and why?

I love the titanosaurs, the giant long-necked sauropods. They are simply awesome — in the literal sense of the word. Colossal creatures heavier than jet airplanes, with necks that could reach several stories into the sky. And the way they are portrayed in the film, the way Gareth celebrates their massive size and scale, it is just mesmerizing. My favorite scene in the film is when the paleontologist, played by Jonathan Bailey, encounters these dinosaurs for the first time and just emotionally gets lost in them. It's beautiful. It's how I would imagine I would react if I saw a real-life giant dinosaur.

HO: If you had to be eaten/killed by a dinosaur, which one would it be and why?

SB: I suppose T. rex, because it would be a quick death. Crushed in those jaws and swallowed.

Editor's note: This Q&A has been lightly edited for style.

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.

Mysterious night lizards survived the giant asteroid strike that ended the reign of the dinosaurs 66 million years ago, despite living right next to the impact site, a new study finds.

Thanks to a new evolutionary analysis, researchers discovered that the little lizards, in the family Xantusiidae, were living around the Gulf of Mexico before and after the asteroid struck what is now Mexico's Yucatán Peninsula. This makes night lizards the only group of land vertebrates known to have survived close to the impact location, and still have members living in the region today.

The dinosaurs' doomsday asteroid was around 7.5 miles (12 kilometers) wide and caused widespread devastation when it hit at the end of the Cretaceous period (145 million to 66 million years ago). The impact was catastrophic for much of Earth's wildlife, triggering the Cretaceous-Paleogene (K-Pg) mass extinction event, in which around 75% of all species died out. However, two lineages of night lizard managed to persist through the disaster, despite likely being close enough to see the impact.

"They would have been all around the margin of the asteroid impact," study lead author Chase Brownstein, a doctoral candidate in the Department of Ecology and Evolutionary Biology at Yale University, told Live Science.

How did night lizards survive amid all the devastation? Researchers aren't sure, but Brownstein noted that they have slow metabolisms, so they wouldn't have needed to eat very often.

The researchers published their findings Wednesday (June 25) in the journal Biology Letters.

Related: Iguanas sailed one-fifth of the way around the world on rafts 34 million years ago

Night lizards grow to only a few inches in length. Often very secretive, the lizards live in specialized microhabitats, like inside rock crevices and dense vegetation, or beneath bark and logs.

Some previous studies suggested that night lizards' "crown" group — the group containing the last common ancestor of all living night lizards — evolved during the age of dinosaurs, which would have meant the animals persisted through the K-Pg devastation. The new study put that hypothesis to the test.

Brownstein and his colleagues reconstructed the ancestry of the three living night lizard genera (Lepidophyma, Xantusia and Cricosaura). They used molecular clock dating to estimate when the night lizards evolved, based on their mutations and the rate at which mutations occur in DNA over time.

The researchers found that the most recent common ancestor of living night lizards emerged during the Cretaceous around 90 million years ago and that night lizards have been living in North America and Central America since around that time, well before the asteroid struck 66 million years ago, according to the study.

The new findings suggest that two night lizard lineages survived the asteroid strike. One of these lineages then gave rise to Xantusia, which ranges from the southwestern U.S. into Mexico, and Lepidophyma, which ranges across parts of North America and Central America. The second lineage then gave rise to Cricosaura and its only species, Cuban night lizards (Cricosaura typica), in Cuba.

Night lizards weren't the only animals to survive the K-Pg mass extinction event. We wouldn't be here today if some of the mammal family tree hadn't lived through the asteroid impact. Avian dinosaurs (birds), fish and plenty of other animals survived, too. However, night lizards are the only known surviving group of terrestrial vertebrates that have remained endemic to — living only in — North America and Central America since the asteroid hit.

Brownstein noted that some lineages of turtles and other lizards in the region probably survived the asteroid in a similar way as night lizards (scientifically named xantusiids) did. However, these other lineages have since disappeared.

"The problem is that they just aren't there anymore," Brownstein said. "So, what's interesting is that xantusiids have persisted and have remained endemic to the region."

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?

Australia is rather isolated today, but around 120 million years ago, the island straddled the polar circle and formed a giant landmass with Antarctica. At that time, dinosaurs lived on this landmass — and thanks to a new study, we now know what their habitat looked like.

New illustrations show that "polar dinosaurs" roamed cool-temperate forests crisscrossed by rivers and carpeted with large ferns. These dinosaurs included small ornithopods — herbivorous dinosaurs with beaks and cheeks full of teeth — and small theropods, which were mostly carnivorous dinosaurs that walked on two legs and often had feathers, one of the study's authors wrote in The Conversation.

"What is now Victoria was once within the polar circle, up to 80 degrees south of the equator and shrouded in darkness for months at a time," wrote co-author Vera Korasidis, a lecturer in environmental geoscience at the University of Melbourne and a research associate at the Smithsonian's National Museum of Natural History. "Despite these harsh conditions, dinosaurs thrived here, leaving behind evidence of their existence at various palaeontological sites."

The amount of sunlight reaching the Antarctic Circle has remained the same over the eons, but the climate was much balmier during the Cretaceous period (145 million to 66 million years ago) than it is today, with temperatures averaging between 11 and 25 degrees Fahrenheit (6 to 14 degrees Celsius) warmer than current temperatures. The Early Cretaceous (140 million to 110 million years ago), in particular, stands out as one of the warmest periods in the past 500 million years of Earth's history, Korasidis wrote, ruling out the existence of polar ice caps.

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

Paleontologists have been studying rocks containing dinosaur fossils from the southern Australian state of Victoria for decades, but they have also been analyzing microscopic spores and pollen grains that may be from plant life that existed near the South Pole during the Early Cretaceous, Korasidis wrote.

For the new study, Korasidis and her co-author Barbara Wagstaff, a pollen and spore specialist at the University of Melbourne, examined nearly 300 pollen and spore samples from 48 sites along the Victoria coast. These samples, which date to between 130 million and 110 million years ago, shed light on the evolution of forests and floodplains where dinosaurs lived, Korasidis wrote.

The researchers published their findings and the first-ever reconstructions of Early Cretaceous polar landscapes Wednesday (May 7) in the journal Alcheringa.

Ancient conifers made up most of the forest canopy, while ferns — specifically, scaly tree ferns (Cyatheaceae), forked ferns (Gleicheniaceae) and another group of primitive ferns (Schizaeaceae) — dominated the understory, according to the study. The researchers noticed an abundance of flowering plants appeared starting around 113 million years ago, which agrees with the timing of the proliferation of flowering plants globally.

"The appearance of flowering plants in the landscape resulted in the extinction of numerous understorey plants," Korasidis wrote in The Conversation. "As a result, by 100 million years ago, the forests of Victoria included an open conifer-dominated forest canopy. Flowering plants and ferns featured in the understorey, alongside liverworts, hornworts, lycophytes and sphagnum-like mosses."

The changing vegetation likely influenced dinosaurs, with many expanding their diet to include flowering plants by the end of the Cretaceous, according to Smithsonian magazine.

The famed Tyrannosaurus rex may have evolved in a very different location from its direct ancestors, new research finds.

The new study builds on earlier research, which suggested that T. rex's ancestors arose in Asia and migrated to North America when sea levels fell, providing a land bridge between the continents. The new study, published Wednesday (May 7) in the journal Royal Society Open Science, provides more evidence that T. rex originated in what is now North America — and this fearsome species' as-yet-undiscovered direct ancestors arose in Asia and migrated across the ancient Earth more than 70 million years ago.

T. rex lived between 67 to 66 million years ago, during the Late Cretaceous period, and could grow to immense sizes — to 12.5 feet (3.8 meters) tall at the hips and up to 41 feet (12 m) long. Most T. rex fossils have been discovered in the U.S. states of Montana and South Dakota, as well as in Alberta, Canada — an area that was once an island continent known as Laramidia that extended through parts of what is now Alaska to Mexico.

T. rex evolved from smaller members of the tyrannosaurid lineage, and the location of where the species originated has long been a hot topic.

Because T. rex has a closer anatomical relationship with Asian tyrannosaurid dinosaurs than it does with North American tyrannosaurids, a 2016 study suggested that T. rex's ancestors likely emerged in Asia and migrated to North America. The new study supports this finding, and suggests that T. rex subsequently evolved in North America.

Related: T. rex researchers eviscerate 'misleading' dinosaur leather announcement

"The geographic origin of T. rex is the subject of fierce debate. Palaeontologists have been divided over whether its ancestor came from Asia or North America," study lead author Cassius Morrison, a doctoral student at University College London (UCL), said in a statement. "Our modeling suggests the 'grandparents' of T. rex likely came to North America from Asia, crossing the Bering Strait between what is now Siberia and Alaska."

The researchers used a model based on where and when various tyrannosaurid species had been discovered, their evolutionary trees, and local climate. They found that T. rex fossils are widely dispersed in Laramidia, and the ancestor of T. rex was present in both Asia and Laramidia, indicating that the T. rex's ancestor likely migrated from Asia to North America between the Late Campanian and the Early Maastrichtian ages, around 72 million years ago.

"This is in line with past research finding that the T. rex was more closely related to Asian cousins such as the Tarbosaurus than to North American relatives such as Daspletosaurus," Morrison said. "Dozens of T. rex fossils have been unearthed in North America but our findings indicate that the fossils of T. rex’s direct ancestor may lie undiscovered still in Asia."

Steve Brusatte, a paleontologist at the University of Edinburgh and co-author of the 2016 study on T. rex's roots, called the new study a "fine scholarly work."

"T. rex was the quintessential American dinosaur: big, bold, ferocious, the ruler of western North America during the final years of the Cretaceous," Brusatte told Live Science in an email. "But it was actually an immigrant. The most iconic American dinosaur was a migrant from Asia."

Gargantuan sizes

The new study also modeled how tyrannosaurids (the group of dinosaurs that T. rex belongs to) and megaraptors (a cousin lineage to tyrannosaurids) grew to such gargantuan sizes. They found that megaraptors — which could grow to lengths of about 33 feet (10 m) — evolved their large size at around the same time as tyrannosaurids.

The researchers suggest that both groups rapidly evolved much larger body sizes than their ancestors following a global temperature peak 92 million years ago. This warming event, known as the Cretaceous Thermal Maximum (CTM), was caused by a spike in atmospheric CO2 and methane as a result of volcanic and tectonic activity, during which sea surface temperatures in some tropical regions may have reached 95 degrees Fahrenheit (35 degrees Celsius).

After the CTM, atmospheric greenhouse gas levels and global temperatures fell. The researchers believe tyrannosaurids and megaraptors may have been able to survive and thrive better than other groups of dinosaurs. This is because other large species of dinosaurs went extinct due to the falling temperatures, leaving an open niche for tyrannosaurids and megaraptors to fill and grow to much greater sizes.

"Our findings have shined a light on how the largest tyrannosaurs appeared in North and South America during the Cretaceous and how and why they grew so large by the end of the age of dinosaurs," study co-author Charlie Scherer, a masters graduate from UCL who is soon to be a doctoral student, said in the statement.

"They likely grew to such gigantic sizes to replace the equally giant carcharodontosaurid theropods that went extinct about 90 million years ago," he added. "This extinction likely removed the ecological barrier that prevented tyrannosaurs from growing to such sizes."

The new study shows how the climate affected even the largest and most dominant dinosaurs, Brusatte said. "It seems like tyrannosaurs were able to get big multiple times independently, when cooler climates promoted increases in size," Brusatte told Live Science. "It was easier to be big when temperatures were cool. The kings of the dinosaurs were not predestined to rule, but were helped along by the climate."

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.

Dinosaurs weren't in decline when an asteroid smashed into Earth and wiped them out, scientists say. Instead, the idea that dinosaur diversity was declining before the asteroid struck 66 million years ago is likely based on faulty fossil data, according to a study that looked at nearly 18 million years of fossil evidence.

Fossil discoveries have long indicated that dinosaurs were shrinking in numbers and diversity prior to the asteroid impact at the end of the Cretaceous period. Previously, some researchers believed this was a sign that dinosaurs were already on the road toward extinction even before the cataclysmic encounter with a space rock. However, this idea has long been controversial, with other researchers arguing that dinosaur diversity was doing just fine at the time of their demise.

"It's been a subject of debate for more than 30 years — were dinosaurs doomed and already on their way out before the asteroid hit?" study lead author Chris Dean, a paleontologist at University College London, said in a statement.

Now, new research published Tuesday (April 8) in the journal Current Biology suggests that the apparent rarity of dinosaurs before their extinction may simply be due to a poor fossil record.

The scientists studied records of around 8,000 fossils from North America dating to the Campanian age (83.6 million to 72.1 million years ago) and Maastrichtian age (72.1 million to 66 million years ago), focusing on four families: the Ankylosauridae, Ceratopsidae, Hadrosauridae and Tyrannosauridae.

At face value, their analysis showed that dinosaur diversity peaked around 76 million years ago, then shrank until the asteroid strike wiped out the nonavian dinosaurs. This trend was even more pronounced in the 6 million years before the mass extinction, with the number of fossils from all four families decreasing in the geological record.

However, there is no indication of environmental conditions or other factors that would explain this decline, the researchers found. All of the dinosaur families were widespread and common, according to models developed by the researchers — and thus at low risk for extinction, barring a catastrophic event such as the asteroid impact.

Rather, the Maastrichtian may have had poorer geological conditions for fossilization, the researchers suggested. Events such as the retreat of the Western Interior Seaway, which once ran from the Gulf of Mexico up through the Arctic, and the rise of the Rocky Mountains starting around 75 million years ago, may have impeded or disrupted fossilization, making it appear as if there were fewer dinosaurs and less diversity during that time.

The team also found that geological outcrops from the Maastrichtian of North America were not exposed, or were covered by vegetation. In other words, rock from this time that might hold dinosaur fossils was not readily accessible to researchers who were searching for the remains. Because half of the known fossils from this period are from North America, the study's findings may have global implications as well.

Among the 8,000 fossil records examined, the team found that Ceratopsians — a group that includes horned dinosaurs like Triceratops and its relatives — were the most common, probably because they inhabited plain regions that were most conducive to preservation during the Maastrichtian. Hadrosaurians — duck-billed dinosaurs — were the least common, possibly due to their preference for rivers. Reductions in river flow may have led to fewer depositions of sediment that could have preserved these dinosaurs, the researchers wrote in the study.

"Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic [252 million to 66 million years ago]," study co-author Alfio Alessandro Chiarenza, a paleontologist at University College London, said in a statement. "If it weren't for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds."

Editor's note: This article was first published on April 8, 2025.

A partnership of companies has announced that it plans to make luxury fashion accessories out of Tyrannosaurus rex "leather" — but researchers say it won't be the real deal.

The T. rex leather will be produced in a lab and is intended to be an "eco-friendly" and "cruelty-free" alternative to traditional leather, according to a statement released by creative agency VML, one of the three companies involved.

The partnership, which also includes biotechnology companies Lab-Grown Leather Ltd and The Organoid Company, plans to base its new material on fossilized T. rex collagen, a common protein that provides structure to skin and other tissues. It will then make the material by engineering cells with synthetic, or artificially created, DNA.

However, dinosaur experts told Live Science that making real T. rex leather would require DNA from the extinct predator, and there isn't any. Furthermore, paleontologists have only found T. rex collagen in bone, not skin, and skin is the basis for leather.

Thomas Holtz, Jr., a vertebrate paleontologist at the University of Maryland, told Live Science that he thought the T. rex leather claim was "misleading" after reading the announcement. "What this company is doing seems to be fantasy," Holtz said in an email.

Live Science approached VML for comment, but it didn't provide one.

Related: 'Dispiriting and exasperating': The world's super rich are buying up T. rex fossils and it's hampering research

DNA begins to decay as soon as an animal dies. Some fragments might survive in the environment for up to a few million years, but researchers haven't found any DNA from the age of dinosaurs. The oldest preserved DNA on record — from an ancient Greenland ecosystem that included mastodons — is about 2 million years old, and T. rex went extinct with the rest of non-avian dinosaurs 66 million years ago.

"We have NO preserved tyrannosaurid DNA (indeed, not Mesozoic dinosaur DNA sequences), so there are no T. rex genes," Holtz said.

Hotz also noted that researchers don't have good tyrannosaurid skin samples, because soft tissues like skin are rarely preserved in fossils. Without good samples, researchers don't know that much about what T. rex skin was like.

"There are a handful of [tyrannosaurid skin] impressions, but that doesn't let us know what the internal tissue was like," Holtz said.

Dinosaur collagen

The upcoming T. rex-themed leather will be based on T. rex collagen, of which there is some in the fossil record. Scientists used to think that all organic components of an animal were destroyed during fossilization. However, in recent years, they've identified collagen in some dinosaur bones. The collagen is preserved through a complex chemical process, and not all of it survives. The researchers Live Science spoke to, who are not involved in the creation of the leather, were skeptical about the use of T. rex collagen for this new material.

Thomas Carr, an associate professor of biology at Carthage College and director of the Carthage Institute of Paleontology in Wisconsin, said that researchers' understanding of T. rex collagen is incomplete because the fossilized polypeptides — the chains of amino acids that make up collagen — are highly fragmented.

"There really isn't much of a template to work from that could accurately reconstruct a collagen molecule that is specific to T. rex," Carr told Live Science. "Second, collagens are pretty generic molecules across all animals and so I'd be very surprised if there was a species-specific sequence that differentiated T. rex — or any dinosaur — from their closest living relatives."

The new lab-grown leather isn't just about extinct dinosaurs; it's also about making the luxury materials industry more sustainable and ethical, according to the statement. The partnership claims lab-grown leather can reduce the environmental impact that can accompany traditional leather production, including the deforestation associated with rearing cattle and the harmful use of chemicals in the leather tanning process. Animals also don't have to be killed as part of the process.

While Carr was "highly skeptical" about the T. rex leather claim, he said it is legitimate to explore lab-grown leather from an ethical perspective, and the partnership's research techniques were interesting. However, he thought it would be more straightforward to focus on living animals like cows and crocodiles, rather than dinosaurs.

"The notion of cruelty-free animal products is a legitimate ethical avenue to explore, so I don't think it needs any exotic 'prehistoric' twist," Carr said.

Before the mid-1960s, it was widely believed that all dinosaurs were cold-blooded, slow-moving animals. But in the summer of 1964, a team of paleontologists led by John Ostrom discovered Deinonychus, a dinosaur equipped with large, sickle-shaped claws; a lightweight body; and strong legs. The fossil suggested the animal was fast and agile.

The discovery showed that some dinosaurs were active and nimble. And so began the "dinosaur renaissance" — a scientific shift that redefined our understanding of dinosaurs by showing that many were faster than previously assumed.

So what was the speediest dinosaur?

"The fastest dinosaur was likely an Ornithomimosauria," Susannah Maidment, a paleontologist at the Natural History Museum in London, told Live Science. These lanky bipedal dinosaurs from the Late Cretaceous period are often described as ostrich-like, with features that suggest they were built for speed.

"Generally, if you have long, slender limbs and your muscle attachments are located near the top of those limbs, then your leg basically functions like a pendulum, which suggests that you can move relatively quickly," Maidment said.

Related: The world's fastest animals

To determine which dinosaur was the fastest, we can turn to biomechanics. In the early 1970s, zoology professor Robert McNeill Alexander pioneered the field of biomechanics by applying physics and engineering to the study of animal movement. By observing modern animals, Alexander discovered a link between leg length and stride length that could be used to estimate an animal's speed.

"The faster an animal walks or runs," Alexander determined, "the longer in general are its strides." Caught up in the dinosaur renaissance, Alexander brought his knowledge of animal locomotion to the study of dinosaurs.

For years, researchers have measured dinosaurs' stride distances and foot size from trackways and compared them to known leg lengths of existing fossils to estimate a dinosaur's speed. However, Maidment said this method is imprecise.

In addition, we don't know if these dinosaurs were moving at their top speed when they left those tracks, noted Eugenia Gold, a paleontologist and associate professor of biology at Suffolk University in Boston. "The really good tracks we get are on softer sediments," Gold told Live Science. "But if you've ever tried to run through mud, you know that you are probably not running at your full speed."

Because trackways offer only partial and sometimes misleading snapshots of dinosaur movement, "we don't have amazingly good data on maximum speed," added William Sellers, a professor of natural science at the University of Manchester in the U.K.

So Sellers turned to evolutionary robotics and biomechanical modeling to get a more accurate picture. By simulating dinosaur movement using computer-generated skeletons and physics-based modeling systems, Sellers predicted how animals likely moved in three dimensions, allowing for more realistic estimates of maximum speed. Since soft tissue, such as muscle and tendons, doesn't fossilize, Sellers had to estimate the size and mass of the muscles. He claims his estimates are reasonable because "vertebrate muscle doesn't vary very much."

Using modern-day animals — including humans, ostriches and emus — Sellers tested and validated his computer models. Knowing the simulations matched speeds in living species allowed him to feel confident the model would give realistic results for nonavian dinosaurs.

Of the five dinosaurs Sellers modeled — Allosaurus, Compsognathus, Dilophosaurus, Tyrannosaurus rex and Velociraptor — Compsognathus was the fastest, clocking in at about 39.8 mph (64.1 km/h), with Velociraptor coming in second, at about 24.1 mph (38.9 km/h). All five of those dinosaurs are theropods — a group of primarily meat-eating dinosaurs that walked on two legs and ranged from small to very large.

"I think they would have had to be very fast because they are very much built that way, and they are meat eaters, and the meat they're going to catch isn't going to be hanging around," Sellers told Live Science. "I'm guessing these small ones were fast moving also because the biggest threat to being a small theropod is probably a big theropod, because you are, after all, tasty."

Compsognathus proved to be the fastest of the dinosaurs Sellers modeled, but he modeled only a small number of dinosaurs. Despite what many people might expect, he found the T. rex was the slowest in the group at 17.9 mph (28.8 km/h). The T. rex was too big to run; its mass would have put enormous strain on its bones, causing them to break. However, other research suggests that T. rex ran at speeds between 10 to 25 mph (16 to 40 km/h).

Like Maidment and Gold, Sellers believes more generally that the fastest was still some type of theropod, but the only way to determine the quickest one would be to model all of them.

Moreover, making the models is highly time-consuming. "You need to reconstruct it in a life-like pose, and then you need to put all the bits that are preserved on," Sellers explained. "And the thing that really takes a lot of time is putting the muscles on. And so it takes six months to a year to actually create one of these things."

In the meantime, Gold offered what's really the true answer to this question, considering birds are living dinosaurs.

"If you want a really straightforward, simple answer, the peregrine falcon is the fastest dinosaur," Gold said. "It dives down through the air. And its fastest speed is 200 mph [322 km/h], and that's faster than anything can fly or run on or swim on the planet."

Editor's note: This story was updated at 10:513 a.m. on April 28 to update Eugenia Gold's title. She is now an associate professor, not an assistant professor, of biology at Suffolk University in Boston.

Fewer Tyrannosaurus rex fossils are available for scientific research because wealthy people are purchasing them for private collections, a new study has found.

Dinosaur fossils are a popular showpiece at many high-end auctions, with near-complete skeletons selling for tens of millions of dollars. However, the private trade in T. rex specimens could be hampering researchers' understanding of the iconic Cretaceous predator, the study found.

T. rex researcher Thomas Carr, an associate professor of biology at Carthage College and director of the Carthage Institute of Paleontology in Wisconsin, showed that there are now more scientifically valuable T. rex specimens in private or commercial ownership than in public museums and other public trusts. Carr told Live Science in an email that the situation was "dispiriting and exasperating" and noted that the ownership of juvenile and subadult specimens was especially worrisome.

"The early growth stages of T. rex are bedeviled by a poor fossil record, and so the loss of them carries the heaviest scientific cost," Carr said. "At the current moment, our knowledge of one of the most basic aspects of T. rex biology is frustratingly compromised by market interests."

Carr published his findings, titled "Tyrannosaurus rex: An endangered species," on April 10 in the journal Palaeontologia Electronica.

Related: Did The Rock buy Stan, the most expensive Tyrannosaurus rex on record?

To better understand the private market's impact on the number of T. rex fossils available to researchers, Carr targeted what he described as "scientifically informative" specimens — skulls, skeletons and isolated bones that researchers would include in studies of T. rex development and variation.

Carr counted the "informative" specimens in public and private ownership by scouring books, museum records, news articles, auction records, anecdotal reports and other sources. He found a total of 61 specimens in public trusts and 71 specimens, including 14 juveniles, in private ownership — likely an underestimate given "the secretive nature" of the private market and year-to-year discovery of new specimens, according to the study.

Commercially sourced specimens sometimes end up in public museums, either on loan or after being purchased by the museum. But Carr found that only 11% of the commercially harvested T. rex fossils end up in public trusts, and that commercial companies are now discovering twice as many T. rex fossils as museums.

Carr also noted that the private sale of dinosaurs isn't limited to T. rex. The luxury fossil market includes all kinds of dinosaurs — the most expensive ever sold was a stegosaurus, auctioned for $44.6 million in 2024. (It is currently on loan to the American Museum of Natural History in New York City). Carr hopes his study will inspire other researchers to examine how the commercial market is impacting other ancient species, like he has done for T. rex.

"My hope is that concerned colleagues will start counting up, and publishing on, the specimens of the species that they study that are lost to the commercial market," Carr said.

Researchers react to T. rex trade

Thomas Holtz, Jr., a vertebrate paleontologist at the University of Maryland, has been researching the changes in Tyrannosaurus during its growth, and said it was "disheartening" to find out that many critical specimens that would help to clarify those changes aren't accessible.

"Much like Carr, I am concerned not merely that there are good specimens which are not accessible to researchers, but especially that juvenile and sub-adult specimens happen to be overrepresented in the commercial samples," Holtz told Live Science.

David Hone, a reader in zoology at Queen Mary University of London, told Live Science that while he'd love to see more specimens in public collections, he wasn't as concerned about the T. rex fossil trade as Carr.

"For a start, there's not that much that can realistically be done about the commercial trade of things like this," Hone said. "And while I'd certainly love to see more specimens in public collections, there are still plenty that can be studied. There are rarer and more important things that are being traded illegally that I'd be more concerned about," he said — referring to Brazilian and Mongolian fossils, including dinosaurs, that are smuggled illegally out of their respective countries.

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 new species of dinosaur with strange claws has been unearthed in Mongolia by paleontologists.

This new genus and species is a therizinosaur, plant-eating, two-legged giants with long claws, and was discovered buried in the Gobi Desert, according to a new study published Tuesday (March 25) in the journal iScience.

Unlike other therizinosaurs, which have three fingers on their hands equipped with long, sharp claws, this new species only has two fingers. This unique anatomy inspired its scientific name, named Duonychus tsogtbaatari, which is Greek for "two digits" and honors the Mongolian paleontologist Khishigjav Tsogtbaatar.

"Many species of therizinosaurs have been discovered, and this group had pretty much been defined by their three-fingered hands sporting large claws," study co-author Darla Zelenitsky, a paleontologist at the University of Calgary in Canada, told Live Science in an email. "To find a specimen with only two fingers/claws was surprising as this was so out of the ordinary for this group of dinosaurs."

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

Therizinosaurs are a group of dinosaurs that lived across what is now Asia and North America during the Late Cretaceous Period (100 million to 66 million years ago). Despite being part of the theropod group of dinosaurs — typically associated with carnivorous dinosaurs like Tyrannosaurus rex — therizinosaurs were herbivorous. These dinosaurs are known for their enormous, sickle-shaped claws, with some species growing talons as long as 20 inches (50 centimeters).

All other therizinosaurs that have previously been discovered, including Therizinosaurus and Beipiaosaurus, have three clawed fingers on their hands, making the discovery of two-clawed D. tsogtbaatari unusual.

"Therizinosaurs are already some of the most unusual dinosaurs out there, but Duonychus tsogtbaatari takes it to another level," study lead author Yoshitsugu Kobayashi, a paleontologist at Hokkaido University in Japan, told Live Science in an email. "This newly discovered species from Mongolia breaks the mold with just two fingers instead of the typical three, offering a rare glimpse into how theropod hands evolved and adapted." "But what truly makes this discovery exciting is the incredibly well-preserved keratinous sheath on its claw — the first such case in a medium- to large-sized theropod dinosaur," Kobayashi added.

The new fossil was unearthed during the construction of a water pipeline in the Bayanshiree Formation in Ömnögovi Province, southern Mongolia. The specimen had excellently preserved hands, with a 3D sheath where the claw — made out of keratin, like our fingernails — would have been. Parts of the arms, spine and hips were also preserved.

"The hands, a hallmark of therizinosaurs, are exquisitely preserved with all the finger and wrist bones intact in this specimen," Zelenitsky said. "Even the keratinous sheath of the claw is preserved revealing how big and sharp its claws really were."

Other species of dinosaur, such as T. rex, had two fingers, but this marks the first time a therizinosaur has been found with fewer than three digits. This species likely evolved to lose one of the three fingers of its ancestors, the study authors suggested.

The researchers think that D. tsogtbaatari may have evolved this unique hand in order to better grip vegetation, allowing for more efficient feeding.

"The loss of the third finger in Duonychus tsogtbaatari might actually have made its remaining two fingers even better at what they were designed for — grasping," Kobayashi said. "Based on the shape of its well-preserved claw and how it curved, Duonychus was likely using its hands to grab onto branches and pull vegetation closer, kind of like how chameleons do today." "We think many therizinosaurs may have used their hands for foraging in a 'hook-and-pull' motion, but Duonychus takes this to another level with its extreme claw structure."

Additionally, Kobayashi suggested that the claws may have played other roles, such as in "defense, courtship, or even play."

The researchers are thrilled by this discovery, as it not only reveals unexpected diversity within therizinosaurs, but also marks the fifth time that a theropod dinosaur group has evolved to lose their third finger.

"While more fossils would help confirm this, all signs point to Duonychus representing a true evolutionary shift, not just a fluke," Kobayashi said. "It’s a remarkable find that reshapes our understanding of therizinosaurs and theropod evolution as a whole."

By disrupting a key gene, scientists made chicken feathers more dinosaur-like — but the results didn't last.

In a new study, researchers inhibited a gene during embryonic development to make chicken feathers more primitive, like the kind of simple tube-shaped proto-feathers that likely first emerged in the ancestors of dinosaurs in the Early Triassic 250 million years ago.

They succeeded — but only temporarily. The chickens showed delayed feather development and naked spots at hatching, but within a few weeks, their plumage looked like any other fowl's.

The study is part of a broader effort to learn how and why feathers first evolved. Researchers had previously altered the same gene to turn scaly chicken feet feathery, but turning back the clock on feather evolution proved harder.

"Our experiments show that while a transient disturbance in the development of foot scales can permanently turn them into feathers, it is much harder to permanently disrupt feather development itself," study senior author Michel Milinkovitch, a professor of genetics and evolution at the University of Geneva, said in a statement. "Clearly, over the course of evolution, the network of interacting genes has become extremely robust, ensuring the proper development of feathers even under substantial genetic or environmental perturbations."

Related: Dark regions of the genome may drive the evolution of new species

Just because the researchers didn't make permanently dino-feathered chickens, it doesn't mean the study was a failure. Milinkovitch and his co-author Rory Cooper, now a research fellow at the University of Sheffield in the U.K., showed how a particular gene, the whimsically named "Sonic Hedgehog" gene, is important in feather evolution. By disturbing this gene, the researchers were able to temporarily disrupt feather formation.

The first feathers were not the complicated, branching features seen on birds today. They were single tubules, shaped like tiny drinking straws. To find out how evolution built everything from soft down to gaudy peacock feathers from these simple tubes, Milinkovitch and Cooper first used a technique called light sheet fluorescence microscopy to examine chicken feather development in the egg. This method uses lasers to image thin slices of a sample.

Feathers start to develop in embryonic chickens nine days after the egg is laid. First, thick spots called placodes pop up all over the developing chicken, the researchers observed. Next, these placodes grow feather buds, which gradually develop into the familiar branching feather form with the help of keratin, the same protein found in human hair and fingernails. The Sonic Hedgehog gene, which is well known to guide embryonic development in animal species, plays a role in all of these steps.

Next, the researchers injected an inhibitor of the Sonic Hedgehog gene into eggs on the ninth day of development to see what would happen. Within days, feather bud growth was stunted. The inhibitor also reduced the complex branching pattern that develops as feathers mature on the embryo.

By day 17 of development, however, the feather growth had partially recovered as the inhibition of the Sonic Hedgehog gene wore off. Chickens that were allowed to hatch had patchy feathers, with some naked spots and other places where soft, down-like feathers had formed, but they did not have outer feathers with a central "rachis," the distinctive quill structure in feathers. By the 49th day of life, however, these chickens molted, and the new feathers that came in developed normally.

The studies show that the Sonic Hedgehog gene has been involved both in the evolution of proto-feathers into today's feathers, as well as in the diversification of feathers into different shapes and sizes across species, the researchers reported March 19 in the journal PLOS Biology.

"The big challenge now," Milinkovitch said, "is to understand how these genetic interactions have changed to allow for the emergence of protofeathers early in the evolution of dinosaurs."

Dinosaurs are the extinct relatives of birds that roamed the lands and seas of ancient Earth. They first appeared around 240 million to 230 million years ago in the Triassic Period, and went extinct around 66 million years ago, at the end of the Cretaceous Period, when a massive asteroid slammed into Earth.

During the Triassic Period, when dinosaurs first evolved, all the continents we know today were clumped together in a single landmass called Pangaea. Over tens of millions of years, Pangaea split apart, eventually coming to resemble the map of the world we know today. Dinosaur fossils have been found on every continent around the globe, including Antarctica.

Some of the most famous types of dinosaurs include Tyrannosaurus rex, Triceratops, Stegosaurus and Velociraptor, many of which were featured in the popular "Jurassic Park" movies. Most of these dinosaurs lived tens of millions of years apart from each other.

Dinosaurs belong to a group of animals known as archosaurs, which also includes modern-day animals such as birds and crocodiles.

5 fast facts about dinosaurs

• The heaviest known dinosaur is thought to be Argentinosaurus, a supermassive titanosaur that lived during the Cretaceous period. It may have weighed up to 180,800 pounds (82,000 kilograms).
• An asteroid wiped out the dinosaurs. The crash left a giant crater around 110 miles (180 kilometers) wide off Mexico's coast.
• The word "dinosaur" means "terrible lizard" in Latin, and it was first made up in 1842 by paleontologist Richard Owen.
• Birds are actually dinosaurs. They evolved from theropods, a group of mostly meat-eaters that included Velociraptor and T. rex.
• Pterodactyls are flying reptiles that lived at the same time as the dinosaurs, but they are not actually dinosaurs.

Everything you need to know about dinosuars

Dinosaur pictures

Discover more about dinosaurs

—A brief history of dinosaurs

—Mesozoic era: Age of the dinosaurs

—What if a giant asteroid had not wiped out the dinosaurs?

A fossil first discovered over 50 years ago has finally been identified as the remains of a pony-sized dinosaur that lived about 166 million years ago.

The fossil was spotted at the base of a cliff on the Isle of Skye in Scotland in 1973, but it was not collected by paleontologists for another 45 years due to its tricky location.

Now, according to a paper published March 6 in the journal Earth and Environmental Science Transactions of the Royal Society of Edinburgh, this fossil — which includes fragments of a spine, ribs, and hip bones — may be the remains of a dinosaur that lived during the Jurassic Period (201.3 and 145.0 million years ago).

This fossil, nicknamed the "Elgol dinosaur" after the village near where it was found, is now considered the most complete dinosaur fossil ever discovered in Scotland, as well as being the earliest ever unearthed there.

Located off the northwestern coast of Scotland, the Isle of Skye is the location of several dinosaur fossils and footprints from the Middle Jurassic period, which is poorly represented in the global fossil record.

Related: Megalodon may have grown up to 80 feet long — far larger than previous estimates

"This is a wonderful addition to the rapidly growing set of Jurassic finds from the Isle of Skye which are enabling us to learn more and more about the rich ecosystem of the time," study co-author Stig Walsh, a senior curator of vertebrate palaeobiology at National Museums Scotland, said in a statement.

The newly identified dinosaur may have been about the size of a pony, and was at least eight years old when it died, according to the researchers.

The fossil was first recorded by paleontologists during field trips between 1971 and 1982, with a 1973 notebook entry mentioning "bones of a dinosaur" in a cliff with a small sketch. The original discoverers didn't realize its significance, and due to its awkward location, it was exceedingly difficult to remove from the ground.

Researchers rediscovered the fragmented fossil in 2015, and itwas eventually excavated and transported from its cliff location in 2018.

"This was a really challenging extraction, in fact we'd previously felt was too difficult to collect the fossil, but I thought it was really important to study it," study lead author Elsa Panciroli, a NERC Independent Research Fellow at National Museums Scotland, said in the statement.

"I was able to persuade the team to give it a try. It took a lot of hard work from a lot of people, but we did it: finally we can confirm and publish Scotland's first recorded and most complete dinosaur, and that makes it all worthwhile."

Paleontologists then studied the fossil using a range of techniques, including micro-CT scanning, which is a non-destructive imaging technique that uses X-rays to create highly detailed 3D images of small objects at a microscopic scale.

The shape and microstructure of the bones, and the fact they were found within the Kilmaluag Formation — a geological formation dating to the Middle Jurassic — indicated that the fossil may be the remains of a cerapodan or ornithopod dinosaur.

Cerapodan dinosaurs are a major group of ornithischian (bird-hipped) dinosaurs, which have a pelvic structure resembling that of modern birds. Ornithopods are one herbivorous sub-group of cerapodans that lived during the Jurassic and Cretaceous periods, and had beaked mouths for cropping vegetation. One of the most well-known groups of ornithopods were Iguanodons, which were one of the first dinosaurs ever named.

If this new dinosaur is indeed ornithopodan, it may be among the earliest ornithischian fossils, and possibly the oldest ornithopodan body fossil in the world.

"Some aspects of the bones indicate that the specimen may be an ornithopod, a group of plant-eating dinosaurs that are best known from the Cretaceous," study co-author Susie Maidment, a paleontologist at the Natural History Museum in London, said in the statement.

"This specimen, however, would already have been a fossil by the time that the better-known ornithopods like Iguanodon and Hypsilophodon were walking the Earth," she said. "Recent research on the fossils of Elgol has revealed a diverse ecosystem of extraordinarily preserved Middle Jurassic animals, and I'm sure there are more exciting discoveries to come."

A known treasure trove of Early Cretaceous fossils has turned up a never-before-seen species of scorpion that lived around 125 million years ago.

The venomous scorpion was larger than many ancient — and modern — scorpion species. Researchers believe it would’ve been a key species in the food chain, gobbling up spiders, lizards and even small mammals that lived in its ancient ecosystem.

It is just the fourth terrestrial scorpion fossil to be found in China and the first Mesozoic-era scorpion fossil found in the country, researchers reported Jan. 24 in the journal Science Bulletin.

Most scorpions from the Mesozoic era (252 million to 66 million years ago) are preserved in amber. Fossilized scorpions are much rarer because these arachnids live under rocks and branches, where they're less likely to be trapped in sediment and fossilize, said study co-author Diying Huang, a researcher at the Nanjing Institute of Geology and Palaeontology in China.

The scientists found the fossil in the Yixian Formation, a hotbed of Early Cretaceous fossils in northeastern China. The team named the new species Jeholia longchengi. "Jeholia" refers to the Jehol Biota, the ecosystem of northeast China in the Early Cretaceous about 133 million to 120 million years ago, and "longchengi" refers to the Longcheng district of Chaoyang, China, where the fossil currently resides.

J. longchengi was roughly 4 inches (10 centimeters) long, making it something of a giant of its time. "Other Mesozoic scorpions are much smaller, most of them less than half [the size] of the new species," Huang told Live Science in an email.

Related: What if a giant asteroid had not wiped out the dinosaurs?

J. longchengi has a pentagonal body and rounded spiracles, which are the openings in its body that allowed it to breathe. These characteristics are similar to those found in some families of modern-day scorpions that inhabit other parts of Asia. But unlike those families, J. longchengi has fairly long legs and slim pedipalps, or pincers, that lack spurs along a segment called the patella.

Fossils of many other animals — including dinosaurs, birds, mammals and insects — have been found in the Jehol Biota, suggesting a complex food web. Larger mammals and dinosaurs may have preyed upon J. longchengi, while the scorpion's diet may have included insects, spiders, frogs and even small lizards or mammals, the researchers wrote in the study.

The scorpion's mouthparts aren't preserved in the fossil, though, so it's hard to know for sure what they ate. Discoveries of additional fossil specimens could clear up the species' role in the ecosystem and its place in the food web, the researchers wrote.

"If placed in today's environment, it might become a natural predator of many small animals, and could even hunt the young of small vertebrates," Huang told China’s state run Xinhua news agency.

The fossil is being stored at the Fossil Valley Museum in Chaoyang, China.

One fateful day 66 million years ago, the dinosaurs — which had inhabited Earth for about 165 million years — got a nasty surprise: A roughly 9-mile-wide (15 kilometers) asteroid crashed into what is now Mexico, triggering tsunamis, wildfires and acid rain and causing vast amounts of debris to block out the sun. As a result, 75% of species on Earth, including the nonavian dinosaurs, died off within months of the impact.

But what if the asteroid had never struck Earth? Would the dinosaurs have continued their reign over the planet? Could they have survived ice ages and evolved to become more intelligent?

According to paleontologists, it's possible that dinosaurs would have continued to evolve and rule Earth. After all, they'd already survived and adapted for 165 million years, which included surviving rising and falling seas, temperature spikes and volcanic eruptions, according to Steve Brusatte, a professor of paleontology at the University of Edinburgh. But this would have made it impossible for our mammal ancestors to evolve the way they did.

Some scientists think dinosaurs would have met their doom anyway because extinctions appear to have outpaced the emergence of new dinosaur species. But Brusatte isn't convinced.

"For those of us who collect fossils of the last dinosaurs, we can see quite clearly that everywhere in the world … there [was] a great diversity and abundance of dinosaurs," Brusatte told Live Science in an email. "It seems remarkably clear to me that dinosaurs were strong, successful, still diverse, [and] still at the top of their game when the asteroid hit."

Related: What happened when the dinosaur-killing asteroid slammed into Earth?

Dinosaurs in an ice age?

But could dinosaurs have lived in frigid conditions, such as ice ages? With the exception of some dinosaurs that lived in snowy climates, the majority didn't. According to Brusatte, some dinosaurs may have fared well under new extreme conditions.

"Many of them had feathers, [so] they could insulate themselves just like mammals can," Brusatte said. In addition, some dinosaurs, such as Tyrannosaurus rex, were likely warm blooded, research finds, meaning they weren't completely at the mercy of a changing climate.

It's also possible that dinosaurs would have evolved new defenses against the cold during extreme weather. Take mammoths, for example, which evolved around 5 million years ago in South Africa. About 800,000 years ago, during the last ice age, some mammoths grew woolly coats as they expanded to the much colder region of Eurasia.

Would dinosaurs have evolved to be more intelligent?

Given enough time, could dinosaurs have evolved into more intelligent creatures? In a 1982 thought experiment, American-Canadian paleontologist Dale Russell wondered whether troodontid dinosaurs could have evolved sentience had they not died in the end-Cretaceous mass extinction. He dubbed them humanoid dinosaurs, or dinosauroids. He based this idea on the fact that one species of troodontid already had a "large brain, stereoscopic vision, opposable fingers and bipedal stature," and might have evolved to have an "encephalization quotient similar to that of Homo sapiens" if it had survived. His collaborator Ron Séguin, an artist and model maker, made a reconstruction, showing a green-skinned creature.

But over the years, paleontologists have dismissed this idea, calling it unrealistic and too anthropomorphic-looking. A 2023 study found that "neither troodon nor any other dinosaur could have begun a primate-like lineage that evolved to a human level of intelligence."

That said, modern-day birds show that dinosaurs may have been fairly intelligent.

"The dinosaurs that live on today — birds — are really smart," Brusatte said. "They actually have more neurons in their brains than mammals, on average. [But] could birds one day achieve human-like cognition? I don't know."

What would have happened to mammals?

Mammal evolution would have faced a severe setback if the asteroid had not hit. Brusatte said that if large dinosaurs had survived, the small, rodent-like mammals that already existed alongside them may not have had the same opportunity to evolve and grow larger.

"I suspect that mammals would have mostly or entirely stayed small for many millions of years more," he said. "Although with cooling temperatures and the last Ice Age, that may have given small mammals — as warm-blooded furry creatures that could handle the cold — an opportunity to get larger, and maybe giant dinosaurs would have gone by the wayside."

Related: Are birds reptiles?

But that doesn't mean that humans would have emerged. "While furry little mammals may have still fared okay, human beings would still likely never have evolved, Paul Sereno, a paleontologist and professor of biology at the University of Chicago, told Live Science in an email.

"We evolved in a mammalian world impossible to have taken place with large nonavian dinosaurs running around," Sereno said. "We are not inevitable."

It's the extinction of land-dwelling dinosaurs, and possibly the extinction of a competing group of mammals, that gave our primate ancestors the opportunity to thrive and evolve, a 2021 study found. If the asteroid had missed Earth, it's likely that humans, at least as we know them, never would have existed.

"History would have been totally different," Brusatte said. "Our exact ancestors surely would have never had their chance to evolve."

Asteroid 2024 YR4 has gone from a potential 'city-killer' to an almost certain near-misser this week as the odds that this large space rock will hit Earth in 2032 rose and then plummeted in a matter of days. Here's what happened and why it matters.

2024 YR4 is around 180 feet (55 meters) wide, with the potential to release 500 times more energy than the atomic bomb that destroyed Hiroshima. A little concern was therefore understandable on Tuesday (Feb. 18), when the likelihood of YR4 hitting us crept up to 3.1% — the highest impact probability NASA has ever recorded for a space object of 2024 YR4's size or larger.

Fortunately, the record-high impact probability was short-lived, and the chances of a strike soon fell to 1.5% and, at the time of writing, dow to 0.28%. None of what played out came as a surprise to astronomers.

The most likely scenario for 2024 YR4 has always been that it will miss us on its closest approach to Earth in 7 years time. That's because, while astronomers have been aware of 2024 YR4 since last year, uncertainty about its orbital path has meant that they couldn't — and still can't — rule out the possibility of a strike. Slight variations in this level of uncertainty were reflected in the shifting odds, which ignited intrigue worldwide.

"Astronomers don't hide and can't hide their discoveries because the sky is open to everyone," Richard Binzel, the inventor of the Torino asteroid impact hazard scale and a professor of planetary sciences at MIT, told Live Science in an email. "So when we discover one of these future visitors that might someday be a close shave, the scientific method of slow careful measurements to get to the answer plays out in a public way."

Related: Potentially hazardous asteroids: How many dangerous space rocks lurk near Earth — and can we stop them?

How threatening is asteroid 2024 YR4?

To categorize the threat posed by asteroids and comets, researchers use Binzel's Torino Impact Hazard Scale. The Torino scale has 11 levels, ranging from Level 0 (no hazard) to Level 10 (global catastrophe).

2024 YR4 reached Level 3 in January 2025 after scientists determined it had a more than 1% chance of hitting Earth. Level 3 asteroids are capable of "localized destruction," which fits 2024 YR4's potential to take out a city.

However, even as 2024 YR4's odds rose to more than 3% — and fell back down to 1.5% — it stayed at Level 3. Binzel said that it's "perfectly natural" for 2024 YR4's odds of impact to "bounce around a bit." However, Level 3 means scientists expect the asteroid will end up with a 0% impact chance with further observations.

Darker skies gave astronomers better views of the asteroid in recent days, following a week of limited visibility around February's full moon. Clearer overnight observations between Feb. 19 and Feb. 20 allowed NASA to refine YR4's odds of impact to 1 in 360, or 0.28%, according to NASA's Planetary Defence blog.

Once the odds dropped below 1%, 2024 YR4 immediately became a Level 1 asteroid, categorized as having "no unusual level of danger" and "no cause for public attention or public concern." In other words, despite chatter surrounding shifting odds, the Torino scale has predicted what would happen all along.

"There's a learning process here, in that it has been pre-baked into the Torino Scale description for Level 3 the exact outcome that is unfolding," Binzel said. "For the moment YR4 has fallen to Level 1, and with further tracking we will see it fall to zero."

What happens if asteroid 2024 YR4's threat level rises?

Asteroids don't necessarily move up or down the Torino levels in order because they're assigned based on both the consequences of a potential impact and the likelihood of an impact.

2024 YR4 fit within the Level 3 criteria of potential "localized destruction" when it had a more than 1% chance of hitting Earth. Level 4 asteroids are larger and capable of more destruction, described as "regional devastation" — so a Level 3 asteroid can't become a Level 4 just with an increased likelihood of impact, according to the scale.

2024 YR4 is likely heading for Level 0 (no hazard). However, if the reassignment to Level 1 hadn't happened, and it turned out YR4 was actually on a collision course for Earth, then it would have leaped straight to the upper levels of the scale reserved for definite collisions, Binzel explained.

"If this asteroid were ever to jump to a higher level, it would go to Level 8, where a 'collision is certain, capable of localized destruction,'" Binzel said when 2024 YR4 was still at Level 3.

However, just like a Level 3 asteroid can't become a Level 4, 2024 YR4 can't get any higher than Level 8 because its size restricts how much damage it can do.

A Level 8 asteroid would be most destructive on land, but also possibly capable of causing a tsunami if it hit offshore. If 2024 YR4 was on course for Earth, it would probably hit somewhere along a "risk corridor" stretching across the eastern Pacific Ocean, northern South America, the Atlantic Ocean, Africa, the Arabian Sea and South Asia on Dec. 22, 2032, according to NASA.

Humanity could try to deflect a large incoming asteroid like YR4, for example by using the orbit of a spacecraft to pull it off course, or using a nuclear explosive to bash it off course, Live Science previously reported.

Binzel noted that decisions on any proactive measures to deflect are the responsibility of a group called the International Asteroid Warning Network (IAWN), which NASA coordinates.

How does 2024 YR4 compare to other space rocks?

2024 YR4 is a rare asteroid. It was the only large asteroid with an impact probability of more than 1% during the period before the odds shifted. A strike from 2024 YR4 would be something like a once-in-a-thousand-year event, based on a NASA asteroid hazard comparison chart.

Binzel compared 2024 YR4 to asteroid Apophis, which reached Level 4 on the Torino scale in 2004 before dropping to Level 0. Named after Apep, the ancient Egyptian god of chaos, Apophis is heading our way in 2029. Scientists are confident it will narrowly miss Earth, but humanity should get a nice view of the giant space rock when it passes in four years' time.

"As it turns out, a very close and safe passage by Apophis in 2029 will be a scientific bonanza and a fascinating view in the sky for billions of people," Binzel said.

Apophis is around 1,100 feet (335 m) long and would have jumped to Level 9 on the Torino scale if it had turned out to be on a collision course with Earth. Level 9 means unprecedented regional devastation on land or the threat of a major tsunami offshore. Only an even larger Level 10 asteroid would be more destructive, according to the scale.

"Level 10 is reserved for the kind of catastrophe that was a bad day for the dinosaurs," Binzel said.

"Tip of the iceberg"

Humanity is continuously improving its space rock detection methods. That means that, as rare as 2024 YR4 is, we are likely to detect more asteroids like it in the decades to come, according to Binzel.

"2024 YR4 is just the tip of the iceberg, as new asteroid discovery surveys are becoming more thorough than ever," Binzel said. "The Torino scale will have its work cut out for it."

Binzel noted that with improved asteroid discovery surveys, we will see many more cases where researchers can detect an asteroid, but don't have sufficient data on its orbital track to be certain of a miss for many decades after its discovery. However, Binzel doesn't see this as a cause for concern.

"Rather than making anyone anxious, by finding these objects that are already out there and by pinning down their orbits, we are becoming more secure in our knowledge that any sizable asteroid is not likely to take us by surprise as an unwelcome guest landing on us."

Anyone who has watched a rooster stalking around a farmyard might agree that there is something very dinosaur-like about birds. That may come as no surprise, given that birds are dinosaurs. But in terms of classification, this raises a question: Since dinosaurs are reptiles, does that mean that birds are reptiles, too?

"I would say that any modern biologist would, or should, say that birds are reptiles," Martin Stervander, an evolutionary biologist and senior curator of birds at National Museums Scotland, told Live Science.

It wasn't always this way. Before the 1940s, biologists relied on a system called the Linnaean method to classify all life on Earth. This approach was developed by Carl Linnaeus in the 1730s, and it works by grouping animals that have similar physical characteristics. Linnaeus determined that all reptiles share two key features: They have scales, and they are ectothermic, or "cold-blooded," meaning they must rely on external sources of heat to regulate their body temperature.

Because warm-blooded, abundantly feathered birds lack these features, "birds were considered their own branch on the tree of life" under the Linnaean system, said Klara Widrig, a postdoctoral fellow in the Vertebrate Zoology Department at the Smithsonian's National Museum of Natural History in Washington, D.C. Linnaean classification accurately describes many relationships and helped to establish the broad branches of the tree of life we use today. Yet this classification system overlooks something that can reveal a lot more about an organism: its genes.

From the 1940s, the ability to examine genetic material gave rise to a new type of classification, called phylogeny. The phylogenetic method groups or separates organisms based on how much of their DNA they have in common. It also allows scientists to compare organisms' DNA to trace their evolutionary history and find shared ancestors.

Phylogeny for birds

Under this system, organisms are grouped into "clades," which are distinct branches on the phylogenetic tree that include all the descendants of a most recent shared ancestor. For example, modern birds are grouped into the Neornithes clade, because they all emerged from a common Neornithine ancestor that emerged 80 million years ago, before the nonavian dinosaurs went extinct. "Clades are a nested hierarchy," Widrig explained. So "if you go further back along the branches of the tree of life, you find that [Neornithes] also belong to the more inclusive clade Theropoda," a group of two-legged and mostly meat-eating dinosaurs that itself is descended from the clade Dinosauria.

Even in the dinosaur age, the defining features of scaly reptiles and birds weren't so distinct. Research suggests that some dinosaurs were warm-blooded and some nonavian dinosaurs sported feathers. Meanwhile, later on we know that birds that looked exactly like modern birds were already stalking the Earth alongside their dinosaur kin 66 million years ago. One of these was the "Wonderchicken" (Asteriornis), a fossil that was described in 2020 by a team that included Widrig. "Say if I got into a time machine and scooped up an Asteriornis and brought it back, everybody would be like, 'Oh yeah, that's just a normal-looking bird.'"

But back to the tree of life: birds' descent from Theropods and Dinosauria is what makes them dinosaurs. Meanwhile, Dinosauria, along with crocodilians, and other lineages like the pterosaurs, are contained within another clade, called Archosauria. This clade, in turn, shares an ancestor with a group called Lepidosauria, which gave rise to all modern lizards, snakes and the tuatara. That shared ancestor was a creature called a sauropsid that emerged about 315 million years ago, and launched the clade by the same name.

Sauropsida was one of two lineages that branched off from the amniotes (vertebrate animals that lay shelled eggs or carry fertilized eggs), the other being the group that evolved into the class Mammalia. Sauropsida, meanwhile, has become synonymous with the class "Reptilia," because within its network of clades upon clades, all reptiles — both living and extinct — are contained.

Related: If birds are dinosaurs, why aren't they cold-blooded?

"All of these guys — snakes and turtles and crocodiles and birds, and the dinosaurs when they were around — they all come back to one common ancestor," Stervander explained, and so under the phylogenetic grouping system, "that simply means that since birds are in [that clade], they are, per definition, reptiles." This is why phylogeny is valuable, because it can reveal that organisms that look very different are, in fact, very close to one another genetically and belong in the same group.

Why don't birds look like other reptiles?

The connections between birds and their scalier kin might have been easier to grasp if there hadn't been a mass extinction event 66 million years ago. "The reason why birds seem so strange compared to the rest of the reptiles that we have alive today is because all the evolutionary intermediate stages are extinct, so we don't have that to compare to," Widrig said. When the asteroid wiped out swathes of life on Earth, it obliterated whole sections of the Archosauria lineage of reptiles, leaving only crocodiles and some avian dinosaurs behind.

Without this void in the once-intricate tree of life, evolution might have ushered relatives into the modern age that would have made birds' reptilian roots more immediately clear. Instead, today crocodiles are birds' closest living relatives, even though they sit far apart on the phylogenetic tree.

To put it into human terms, "if all non-human primates were to suddenly go extinct today, our closest living relatives would actually be rodents and rabbits," Widrig said. They would be closest to us on the remaining branches of the tree of life, and our shared mammalian ancestry might be harder to accept.

If it still seems strange to think of birds as reptiles, it might partly be because of those Linnaean roots, which continue to shape our colloquial understanding of what a reptile is. "It's not until around the [19]40s where genetic evidence actually clarified where birds sit [on the tree of life]," Stervander said. "People had been referring to reptiles for almost two centuries before that. I think that's why there's been some unwillingness to redefine what we call the reptile."

But modern science is changing that, revealing unexpected connections in the tree of life — and opening our eyes to skies filled with modern feathered, flying reptiles.

Remains of the very first dinosaurs on Earth may be buried deep beneath the Sahara desert and Amazon rainforest, a new study suggests.

If found, these fossils could trace the history of dinosaurs much further back than 230 million years, the age of the oldest dinosaur bones unearthed to date. Such a discovery would also radically change scientists' understanding of where — and how — dinosaurs first evolved.

"Dinosaurs are well studied but we still don't really know where they came from," lead author Joel Heath, a doctoral student in Earth sciences at University College London (UCL) in the U.K., said in a statement. "The fossil record has such large gaps that it can't be taken at face value."

Fossils recovered to date suggest dinosaurs first appeared in the southernmost regions of the ancient supercontinent Gondwana, which included present-day South America, Africa, India, Australia, New Zealand, parts of the Middle East and Antarctica. Researchers regularly find fossils in southern Brazil, Argentina and Zimbabwe that indicate dinosaurs inhabited the southern polar region toward the middle of the Triassic period (251.9 million to 201.3 million years ago).

Related: Giant horned dinosaur's fossils were destroyed in WWII — but photos reveal it was an unknown species

Yet stark differences between some of these fossils may indicate that dinosaurs originated earlier in the Triassic period than we thought, evolving distinct characteristics as they spread across the world, according to the new study, published Thursday (Jan. 23) in the journal Current Biology.

New origin story?

For the study, Heath and colleagues simulated the distribution of the very earliest dinosaurs using a computer model. They incorporated known evolutionary relationships between early dinosaur groups, as well as climatic and geographic barriers that may have blocked the movements of these prehistoric reptiles. The researchers also accounted for gaps in the fossil record by treating areas where no fossils have been found so far as "missing information," rather than as areas where dinosaur fossils simply don't exist.

Their results showed that the earliest dinosaurs likely emerged in Gondwana's hot equatorial regions, which include present-day Amazonia, the Sahara desert and the Congo basin. These dinosaurs would have been much smaller than their descendants — similar in size to chickens or dogs, according to the statement.

"Our modeling suggests that the earliest dinosaurs might have originated in western, low-latitude Gondwana," Heath said. "This is a hotter and drier environment than previously thought, made up of desert and savanna-like areas."

The reasons why researchers haven't found fossils in these regions are that they are overlooked and often inaccessible, Heath said.

The recent discovery of fossils belonging to the oldest-known dinosaur in North America — a 230 million-year-old, chicken-size raptor — bolsters the new findings, because it showed that dinosaurs existed in the Northern Hemisphere at this time. Paleontologists previously assumed that dinosaurs were confined to the Southern Hemisphere, but the groundbreaking discovery rejigged the map to make the equator a midpoint, rather than a northernmost boundary.

Proposing that dinosaurs first evolved near the equator is less far-fetched now that their distribution around 230 million years ago has been rewritten, according to the statement. If dinosaurs were present in the Northern and Southern Hemisphere, the equatorial regions can't have been closed off to them, Heath told New Scientist. "They have to have been crossing that region," he said.

The new study suggests the earliest dinosaurs were adapted to hot temperatures and arid climates. "Out of the three main dinosaur groups, one group, the sauropods, which includes the Brontosaurus and the Diplodocus, seemed to retain their preference for a warm climate," study co-author Philip Mannion, a professor of paleobiology at UCL, said in the statement.

The two other groups, the theropods and ornithischians, may have evolved the ability to generate their own body heat, and therefore moved closer to the poles, Mannion added.