A fossil that sat in a museum collection for over a century is a previously unknown species of predatory dinosaur, researchers have found. The discovery could help scientists solve a longstanding mystery about how some of the Cretaceous period's most formidable hunters spread around the globe.

The dinosaur lived on what is now the Isle of Wight in southern England about 120 million years ago. It belonged to a group of two-legged carnivores called megaraptors, which are related to tyrannosaurs. But unlike tyrannousars, megaraptors are thought to have relied on their powerful arms and large curved claws to attack prey and defend themselves.

The newly identified species was described in an Oct. 14 study in the journal Royal Society Open Science. It is the first megaraptor identified in Europe, filling an important gap in the fossil record of a group whose evolutionary history remains poorly understood.

"It is a real mystery that this fossil was overlooked for so long, sitting in a drawer for nearly 100 years," study first author Cassius Morrison, a researcher in the Department of Earth Sciences at University College London (UCL) said in a statement. "Lots of bones are found on the Isle of Wight — who knows what else is waiting to be discovered."

Unconquered female warrior dinosaur

The discovery of the megaraptor began in 1924, when an amateur fossil collector discovered a dinosaur skull fragment on the Isle of Wight. The specimen eventually entered the collections of London's Natural History Museum, but it was largely forgotten.

Recently, researchers revisited the fossil as part of a study on dinosaur braincases. To identify the animal, the researchers used micro-CT scanning to examine the fossil's internal structure and build detailed 3D digital models of the space that once held the dinosaur's brain.

The researchers then compared the animal's anatomy with that of other meat-eating dinosaurs, including tyrannosaurs, spinosaurs and other theropods (the group of two-legged, mostly meat-eating dinosaurs). Several features differentiated the unknown specimen, including an almost oval opening where the spinal cord entered the skull and an unusual, hourglass-shaped ridge at the back of the braincase.

Computer-based evolutionary analyses placed the fossils within the Megaraptora family tree, supporting the idea that the skull represented a never-before-seen species. The researchers named the dinosaur Invictibellatrix amberina, combining the Latin words "unconquered" and "female warrior" for the genus name, while amberina refers to amber found in the rocks associated with the fossil.

Megaraptors lived between roughly 125 million and 66 million years ago and varied considerably in size. While early members were relatively small, some later species became enormous predators. Maip macrothorax, discovered in Argentina, may have reached up to 33 feet (10 meters) long and weighed as much as an elephant. Based on comparisons with related dinosaurs, I. amberina was much smaller, likely around 10 to 13 feet (3 to 4 m) long and standing roughly 5 feet (1.5 m) tall. The researchers estimated it weighed around 440 to 660 pounds (200 to 300 kilograms), making it one of the smallest known megaraptors.

"It was not the apex predator of its time, but for humans this dinosaur would have been more dangerous than a T. rex," Morrison said. "We would have been perfectly sized prey, about a third of their body weight. They definitely would have chased us."

Although the newly described fossil doesn't preserve the animal's arms or claws, its closest relative suggests that its claws may have measured around 4 to 8 inches (10 to 20 centimeters) long. The researchers also suggested I. amberina may have been feathered, though that feature can't be determined directly from the specimen.

A missing link in the dinosaurs' globetrotting

Scientists have long suspected that megaraptors originated in Asia before spreading to other parts of the world, eventually becoming the dominant predators across the southern supercontinent Gondwana, which included present-day Africa, South America and Antarctica. But a lack of European fossils left an important gap in verifying this migration route.

The new study's evolutionary models suggest that I. amberina descended from Asian megaraptors that dispersed into Europe around 130 million years ago. From there, members of the group may have moved through what is now Africa and further into Gondwana via temporary landbridges and temporary land connections across the shallow Tethys Ocean.

"This new species is the first proof we have that megaraptorans were also present in Europe and that they reached Gondwana this way rather than island-hopping further south," study co-author Charlie Scherer, a doctoral student at UCL Earth Sciences, said in the statement.

However, the specific route these animals took over millions of years is still unknown. The researchers also cannot yet explain why megaraptors disappeared from northern areas, but changes in climate or competition with other predatory dinosaurs may have contributed. More research on other megaraptor fossils like I. amberina could help uncover more clues.

"Work like this shows the exceptional value of working with historical museum collections where there are still many discoveries to be made," study co-author Paul Barrett, a researcher of dinosaur evolution at the Natural History Museum in London, said in the statement.

Paleontologists in China have discovered a small Jurassic bird that was likely a land-based predator — like a carnivorous pheasant with killer claws. It had some features of birds and others of dinosaurs, suggesting that the earliest birds had a greater diversity of lifestyles than previously recognized.

Jurassic birds first emerged 150 million to 148 million years ago, and fossils of them are rare, so experts are just starting to understand how early birds diversified and evolved the ability to fly.

The researchers discovered the newly identified Yuezhuornis yangyuanensis in 2024, in the fossil assemblage known as the Upper Jurassic Zhenghe Fauna in southeastern China. It lived 150 million to 148 million years ago, roughly when birds started to appear in the fossil record. The team published their findings Wednesday (Oct. 14) in the journal Nature.

Analysis of the fossilized skeleton revealed the animal was small and weighed about 1.8 pounds (0.8  kilograms). "It was probably as large as a crow," Min Wang, a researcher at the Chinese Academy of Sciences, told Live Science via email.

Y. yangyuanensis had a mix of features seen in birds and predatory Deinonychosauria dinosaurs, such as Velociraptor, which are known for their sickle-shaped toe claws. It had deinonychosaur-like hyperextensible toes, with forelimbs that were roughly one-third shorter than its hind limbs. This is odd because modern birds and many other Jurassic paravians — the group that includes bird-like dinosaurs, including the ancestors of birds as well as modern birds themselves — have long forelimbs, linked to giving wings more lift force for taking off.

Y. yangyuanensis also had slender cranial elements and sparsely spaced teeth. These features, alongside the curved claw-like toes that were capable of securing prey, suggest that the animal's diet included meat.

"Its key anatomical features are the combination of dinosaurs' and birds' features: for instance, its teeth, pectoral gird, and especially the hyperextensible, 'sickle-clawed' second pedal digit are similar to that of dinosaurs," Wang said. Meanwhile, he said its slender cranial bones and bird-like pelvis are comparable to early birds.

This combination of features suggests that "the morphological gap between birds and dinosaurs is much smaller than we thought," he added.

Comparisons with 377 living bird species showed that the limb proportions of Y. yangyuanensis were most similar to those of terrestrial birds.

Wang suggested that Y. yangyuanensis was a flightless bird, but not one specialized to live in trees or wade in the swamps in the region. It was a small carnivore, with similar proportions to a pheasant, that was well adapted for running. "I think there are no directly comparable modern birds," he said.

The mosaic of features hints that Y. yangyuanensis may have occupied an ecological niche that was rarely utilized by early birds, and that there wasn't a systematic progression toward flight optimization, Wang said.

Despite being flightless, Wang and his colleagues place Y. yangyuanensis closer in the evolutionary tree to modern birds than to Archaeopteryx, one of the world's first proto birds, which lived about 150 million years ago and is thought to have been able to fly.

This adds to evidence that "the ability to fly arose not once, but several times among disparate groups of carnivorous dinosaurs that are closely related to birds," wrote Fernando Novas, a paleontologist at the Felix de Azara Natural History Foundation in Buenos Aires, Argentina, who wasn’t involved in the study, in an accompanying article in Nature. This includes flight evolving in early birds and in scansoriopterygid dinosaurs, which had membranous folds like the wings of bats, and the four-winged microraptors. Y. yangyuanensis seems to have taken a different road, eschewing the flying ways of its relatives.

"It highlights the extraordinary breadth of ecological and morphological diversification that took place close to the origins of avialans," Wang said.

A newly discovered platypus-like creature is the largest-known mammal relative from the entire Jurassic period, a new study finds — although it still only weighed as much as a Chihuahua.

The critter, which hunted salamanders in the freshwater lakes and rivers of what is now Inner Mongolia, China, lived during the mid-Jurassic between 168 million and 163 million years ago. It seems to be the earliest known mammal-type animal that lived a semiaquatic life.

Researchers unearthed the delicate and detailed fossil in 2016, which revealed that the animal likely weighed about 2.2 to 4.4 pounds (1 to 2 kilograms). It was large for a mammal relative during the Jurassic, but its name, Megacauda sungei, was inspired by its tail: Megacauda means "big tail." The discovery was detailed in a study published on Wednesday (Oct. 7) in the journal Nature.

The furry predator had a mix of features seen in modern-day animals, with a broad, flattened tail that marks it as a powerful swimmer, and short hind legs with relatively long feet.

"It's like a chimera," study co-author Zhe-Xi Luo, a paleontologist at the University of Chicago, told Live Science. "The back half of this animal is very much like a platypus. As are the limbs, which would be capable of swimming or digging tunnels in river banks."

But the teeth "are definitely not like a platypus," Luo said. It possessed robust canines and shearing cheek-teeth that would cut and chew meat in a different way from modern carnivorous mammals. "It's a predator with gigantic and very specialized canines," Luo said. "So, it's partly otter-like and partly platypus-like."

A revealing fossil

Tiny bits of vertebrate bones found in what would have been the animal's stomach and the surrounding fossil beds hint that M. sungei dined on salamanders, Luo said.

He added that M. sungei may have sheltered in burrows on land in the temperate plant-filled climate, and hunted in lakes and rivers for fish and invertebrates.

Another notable aspect of the fossil is its throat. Modern mammals, including humans, have hyoid bones in the throat arranged in a "U"-shaped saddle. These help us use throat muscles to swallow chewed food one chunk at a time, instead of gulping down huge bites or whole prey. The structures also enable babies to suckle their mother's milk.

M. sungei seems to have had the apparatus needed to do this, study co-author Thomas Martin, a paleontologist at the University of Bonn in Germany, told Live Science.

"This is an incredibly important evolutionary innovation," Luo said, adding that this capability is one of the things that helped early mammals diversify into carnivores, insectivores, herbivores or omnivores to take advantage of all sorts of foods.

Finding this in M. sungei suggests that the apparatus needed for suckling milk and swallowing had already evolved by the Middle Jurassic (around 174 million to 164 million years ago), Martin said.

This is before marsupials like kangaroos and placental mammals like primates and bears are thought to have diverged from each other 160 million years ago, after descending from an egg-laying common ancestor that lived approximately 180 million years ago.

"Now we push the history of it back to before the split of modern marsupials and modern eutherian [placental] mammals," Luo said.

"Neonatal suckling behaviour was previously thought of as being a hallmark of advanced mammals, but it now appears to have evolved well before then, in the common ancestor of docodontans and mammals at least 165 million years ago," said Sue Hand, a vertebrate paleontologist at the University of New South Wales in Australia who wasn’t involved in the study.

M. sungei is from an extinct lineage of docodonts, which are relatives of mammals from the dinosaur-dominated Jurassic and Cretaceous periods, living between about 200 million and 120 million years ago.

Docodonts adapted to a wide variety of habitats. For example, there was the Jurassic tree-dwelling shrew-like docodont called Microdocodon gracilis, and Docofossor brachydactylus, a tunnel-digger with shovel-like paws. Luo was also part of the team that described a semiaquatic "Jurassic beaver", Castorocauda lutrasimilis, which lived 164 million years ago.

"It seems that an aquatic lifestyle arose often in early mammal-like species," said Tim Flannery, a mammalogist at the Australian Museum Research institute who wasn't involved in the work.

If anything, the newly described "spectacular fossil" shows that docodonts were wide-ranging during the dinosaur age, Hand told Live Science in an email.

"This very detailed study adds to accumulating evidence that mammaliaforms occupied a wide range of ecological niches long before the evolution of living mammals," Hand said.

Mammals first appeared on Earth over 200 million years ago, scuttling around alongside the dinosaurs as little mouse-sized creatures. But after the asteroid hit 66 million years ago, it was their time to shine ‪—‬ and the Age of Mammals began.

But the path to understanding our own branch of the animal kingdom hasn't been straightforward. In this excerpt from "The Story of the Mammals in 25 Discoveries" (Columbia University Press, 2026), author Donald R. Prothero looks at a time when philosophers and early naturalists believed giants roamed the Earth and explores the idea that extinction was heresy.

Many cultures around the world have a mythology that includes legends about gigantic races of humans that lived on Earth in the dark mysterious past. They may have fought against the gods, or they may have been destroyed by floods. These stories were reinforced by the discovery of gigantic bones, much larger than those of any living human, all over the Mediterranean and Europe.

The Greek philosopher Empedocles (492-432 BCE) reported gigantic bones from Sicily, supposedly remnants of a race of giants. The Roman historian Pliny the Elder (23-79 CE) mentioned fossil ivory in the ground, and according to the Roman historian Suetonius (69- 122 CE), Emperor Augustus owned a collection of large bones that had been found on the island of Capri, near Pompeii. The skulls of elephants, with their huge central opening in front (for the trunk), were thought to be the skulls of the one-eyed cyclops.

In the Middle Ages, these huge bones were again attributed to gigantic humans or other monsters (Genesis 6:4) that were drowned in Noah's flood. Giant tusks from Siberia were thought to be the horns of the mythical unicorn or the tusks of dragons. In some places gigantic teeth or vertebrae of mammoths were revered as relicts of saints. Nearly every possibility was suggested except that they were the bones of extinct elephants.

In the early seventeenth century, some giant bones dug up in a sand pit near Langon in southeastern France were exhibited around France as the remains of the giant Teutons, Germanic tribes that once roamed Gaul and were defeated by the Romans in 101 BCE.

But in 1613 the famous anatomist Riolan attacked the prevailing interpretation, suggesting that they were the bones of an elephant. This generated a raging controversy between physicians and anatomists and the barber-surgeons who called them gigantic human bones. Others thought they were hoaxes or generated by mysterious "plastic forces" (vis plastica in Latin) that percolated through Earth. Still others attacked the anatomists for questioning the biblical account of giants on Earth. The controversies died down in 1618 without being resolved, and for the next two centuries most people continued to interpret new finds as gigantic humans.

The giant bones that kept turning up in the New World were also a source of much mystery and consternation. The Native American tribes usually attributed them to giant monsters fought by their ancestors and incorporated them into their folklore. When these bones were first seen by European settlers, they were thought to be the bones of gigantic humans that roamed the earth in biblical times. Others thought that the giant tasks so revered by the Native Americans were the works of Satan, placed there to tempt the believer.

In 1519, the Spanish explorer and conquistador Hernan Cortez received a bone of a "giant," a gift from the friendly Tlascalan tribe of Mexico during the conquest of the Aztecs. He sent it back to the King of Spain as proof that giants at once lived in the New World. In 1706, the Reverend Cotton Mather of the Massachusetts Bay Colony pronounced them to be "the remains of godless giants drowned in Noah's Flood." He sent some bones to the Royal Society in London to have them certified as evidence of this "wicked giant" because biblical scholars were calculating Adam's height at 123 ft. 9 in.

The Royal Society never pronounced an opinion on these bones, although by that time many members were becoming skeptical of the literal interpretations of Genesis. The stifling effect of religious dogma about giants and Noah's flood was complicated by another idea: the notion of Divine Providence. An omnipotent, benevolent God would never allow any of his creatures to become extinct. As the poet Alexander Pope wrote in An Essay on Man (1734), "who sees with equal eye, as God of all, a hero perish, or a sparrow fall."

The prevailing concept was that of a "great chain of being" that linked the animals to man to the angels to God. Breaking any link in that chain implied the destruction of the whole chain. In the same poem, Pope also wrote: "Where, one step broken, the great scale's destroy'd; From Nature's chain whatever link you strike, Ten or ten thousandth, breaks the chain alike."

By the late 1700s, however, it was becoming more and more apparent that many of the recently discovered fossils had no living counterparts. Remote corners of the world were being explored, and although many new and surprising beasts were discovered, clearly the gigantic beasts were not hiding in South America or Africa or the East Indies. Many strange fossils, such as the bones of hippopotami in Paris and London, were clearly related to tropical animals, but it was assumed that these bones had been washed from the tropics during the Great Flood.

The notion of extinction was still blasphemous. The New World soon provided unequivocal evidence that these large bones were not simply gigantic humans. In 1739, Charles le Moyne, the second Baron de Longueil, left Montreal with French and Indian troops to fight the Chickasaw Indians along the Ohio River. Somewhere along the Ohio he found the remains of what appeared to be three elephants. When the war ended in 1740, le Moyne collected the bones and shipped them to New Orleans and ultimately to Paris, where they came to the attention of French naturalists.

In the 1740s and 1750s, English settlers in the region sent more of these bones from Big Bone Lick, Kentucky, off to England and also to Benjamin Franklin in America. Most of the bones (especially the tusks) were clearly like those of elephants and mammoths, but the teeth were puzzling. They were clearly unlike any living elephant, yet they were part of an animal of elephantine size. (We now know that these were specimens of the American mastodon, Mammut americanum.) Franklin speculated that the teeth were reminiscent of a carnivorous animal, although he and others later decided it was a vegetarian.

In 1769, the famous British anatomist William Hunter took the carnivory suggestion seriously and suggested this was not a true elephant but a "pseudelephant" or "American incognitum" (Latin for "unknown") that had independently developed ivory tusks:

"This monster, with the agility and ferocity of a tiger . . . cruel as the bloody panther, swift as the descending eagle, terrible as the angel of night. . . . And if this animal was indeed carnivorous, which I believe cannot be doubted, though we may as philosophers regret it, as men we cannot but thank Heaven that its whole generation is probably extinct."

This very precocious suggestion was still not accepted by naturalists of the time. Nevertheless, remains of the "incognitum" and also of the Siberian mammoth (including frozen carcasses with hair and skin) were turning up again and again. Georges Louis Leclerc, the Comte de Buffon (1707-1788), concluded in his Théorie de la terre in 1749 that although most of the supposedly extinct animals were hiding somewhere in an unknown region, it was likely that the large terrestrial mammals such as the mammoth and "incognitum" had actually perished.

By 1778, Buffon was relating their disappearance to his ideas of violent cataclysms in Earth's early history. During this time the climate was warmer and polar regions had once been tropical, so "elephants" (meaning mammoths) could live in Siberia. This implied a nonbiblical Earth of much greater antiquity. Buffon suggested it was as much as 75,000 to 3,000,000 years old, rather than the 6,000 years demanded by most literalist biblical scholars.

Naturally, such revolutionary ideas were not popular with the theologians in the Sorbonne. Buffon was protected by the king, however, so he was not persecuted for his heresy, although his ideas were not widely accepted either. The fact of extinction was finally proved by one of the greatest scientists of all time, the Baron Georges Cuvier (1769-1832).

Jean Leopold Frederic Georges Cuvier was an impressive man. Tall of stature, he had a "massive" head crowned by a large mane of hair. One admirer wrote that his head "gave to his entire person an undeniable cachet of majesty and to his face an expression of profound meditation." After his death, scientists weighed his brain and found that it was a massive 1830 grams [4 pounds], more than 400 grams [14 ounces] above average, and 200 grams [7 ounces] heavier than any brain ever measured at that time.

More important, he was one of the most brilliant men of his time, with a command of many subjects, some of which he invented all by himself. Before Cuvier, natural history was a field that resembled stamp collecting, with many amateur naturalists compiling long lists and descriptions of new species without analyzing the similarities in their anatomy. Cuvier almost single-handedly revolutionized natural history by dissecting many different animals and discovering their underlying similarities and differences.

This became the foundation of comparative anatomy, a subject that has been fundamental to biology ever since. Naturalists and explorers sent him their fossil bones, and he was the first to correctly describe many types of extinct animals. Cuvier solved the mystery of the puzzling fossil teeth called the "Great Incognitum" and recognized them as the teeth of the elephant-like mastodons. He also correctly deciphered the huge marine lizards we now know as mosasaurs.

For this reason, he is also considered to be the founder of vertebrate paleontology. Cuvier is most famous for his "law of correlation of parts," wherein he discovered that certain types of anatomical features tend to be associated. If you are a flesh eater, you will have sharp teeth and claws; if you are a plant eater, you will have flat grinding teeth and hooves; and so on. Using this law, paleontologists have been able to reconstruct whole animals from just a few key bones because the other parts of the anatomy are so predictable.

Excerpted from The Story of the Mammals in 25 Discoveries: Amazing Fossils and the People Who Found Them by Donald R. Prothero. Copyright (c) 2026 Donald R. Prothero. Used by arrangement with the Publisher. All rights reserved.

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A predatory bird-like dinosaur with four wings discovered in China adds evidence to the idea that flight evolved several times in different dinosaur groups.

The exceptionally well-preserved feathered dinosaur, which has been named Norellraptor barsboldi, was 3 years old when it died and measured just 21 inches (57 centimeters) long. It was found in the Early Cretaceous Jiufotang Formation in northeastern China, which dates to between 145 million and 100 million years ago.

N. barsboldi had the sharply curved predatory teeth and claws you'd expect of a little, generalist predator and was probably eating early mammals, lizards, amphibians and juvenile dinosaurs, said Scott Hartman, a vertebrate paleontologist at the University of Wisconsin-Madison who wasn't involved in the study. "It wouldn't have been attacking any large dinosaurs. That would be like mosquitoes attacking battleships," he told Live Science.

N. barsboldi was a microraptor. Microraptors were close relatives of birds but not their ancestors; birds belong to a neighboring clade called Avialae. Fossils show that both microraptors and early bird-winged animals in the Avialae clade ‪—‬ such as Archaeopteryx, which lived in the Late Jurassic, about 150 million years ago ‪—‬ had feathers. The puzzle has been whether flight originated in an ancestor of both of these groups or if feathers — and potentially flight — evolved more than once.

The description of N. barsboldi by Andrea Cau, a paleontologist at the OPHIS Paleontological Museum and Herpetological Center in Italy, and his colleagues adds evidence to the latter theory. The team's analysis found that around 30% of the 194 anatomical changes identified across microraptor evolution also evolved in the bird lineage. Aside from feathers, these changes included the fusion of bony projections to the ribs that created a rigid torso, forelimb bones that were relatively robust compared with the hind limbs, and an ulna (the primary weight-bearing bone for a wing) that was longer than the humerus.

However, the team's comparisons with other fossils revealed that the order in which these shared features evolved was different in the two groups. They reported the findings Tuesday (Sept. 29) in the journal Nature Communications.

"This demonstrates that microraptors acquired traits convergent with the early evolutionary stages of true birds, albeit through a distinct evolutionary pathway, supporting the hypothesis that flapping flight evolved independently in non-avialan dinosaurs and birds," said Rui Pei, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences who wasn't involved in the work.

"I'm very happy that they've come to the conclusion that there were probably independent origins of flight amongst various groups," Hartman said. "I strongly agree with them."

Even though microraptors had four wings, many of their features were similar to those of modern flying birds. Therefore, "it is reasonable to expect that these non-avialan theropods were capable of behaviors comparable to those of modern avian species," Pei told Live Science by email.

Hartman suggested that microraptors might have done a mix of gliding and flapping. "I doubt they could climb trees like a squirrel to gain height because their forelimbs don't have that range of motion," he said. However, they might have been able to take off after running down a slope, and rather than gliding down from trees, they might have leapt from hills or cliffs, Hartman added.

"There are a bunch of features, like a large well-ossified [bony] sternum or breastbone that could allow for larger pectoral muscles, so they probably have a pretty solid downstroke, which is what generates the thrust to keep it going forward," Hartman said.

The hind wings would have been held directly under the body for stabilizing flight, braking and allowing for rapid control of tight turns. "These are clearly little predatory buggers," he said. "If you're leaping onto things or dropping onto things, that kind of control would be pretty important. It's always best to surprise animals by landing where you planned to rather than somewhere you didn't plan to."

It's also possible that the wings had other purposes, such as demonstrating fitness to mates or warming eggs on a nest, he said.

Rare fossils discovered in Japan more than 30 years ago are from a new species of armored dinosaur — one whose ancestors likely reached Asia by trekking across a land bridge, a new study finds.

The newly named dinosaur, a type of nodosaurid, is now one of just three species of its kind found in Asia to date. The scarcity of nodosaurids in Asia, and the fact that the newly described beast is similar anatomically to those from North America, hint that its species likely arose from a migration from North America to Asia via the Bering Land Bridge, an ancient strip of land that connected present-day Alaska and Russia, researchers reported in the February 2027 issue of the journal Cretaceous Research.

"It's super cool to see [the specimen] getting a new look and a new name," said Victoria Arbour, manager of research and collections at the Royal B.C. Museum in Canada. Arbour was not involved in the new work.

Nodosaurids are armored dinosaurs covered in bony plates. They are closely related to ankylosaurids, but they lack the heavy tail clubs ankylosaurids used to protect themselves from predators. Nodosaurid fossils have primarily been found in North America and Europe, though a few have been uncovered in Asia.

In the new study, a team of researchers revisited one such fossil specimen originally discovered in 1995 on Hokkaido, the northernmost main island of Japan. The scientists performed computed tomography (CT) scans of the fossils, which are somewhere between 93 million and 100 million years old, and include the back of the skull, part of the lower jaw, and several teeth and bony plates.

CT scanning enables researchers to make digital 3D models of specimens, and "lets you just get more information than you'd be able to have otherwise, because you can look inside without breaking [the fossil]," Arbour told Live Science.

Based on the CT scans and an anatomical analysis, the team determined that the fossils represented a new species of nodosaurid, which they dubbed Nipponopelta yezoensis. "Nippon" refers to Japan, and "pelta" means "shield" in Greek. "Yezo" is the traditional name for Hokkaido.

N. yezoensis is closely related to North American nodosaurids, the team found. The dino's ancestors may have migrated from North America to Asia via a land bridge in what is now the Bering Strait 100 million to 110 million years ago.

Coastal dinosaur?

A separate team of scientists originally uncovered the N. yezoensis specimen in marine sediments — rocks that formed under ancient seas. Nodosaurids didn't live in the ocean, so the findings suggest that after the animal died, its corpse may have been swept out to sea along a river or estuary and eventually sank to the ocean floor.

Several other nodosaurid fossils have been found in similar marine deposits, suggesting the creatures lived along coastlines. That may have helped them migrate along the Bering Land Bridge and disperse by following the coast, study co-author Darla Zelenitsky, a dinosaur paleobiologist at the University of Calgary, told Live Science.

But just because nodosaurids are most commonly found in coastal environments doesn't mean that they couldn't have lived further inland as well, said Jordan Mallon, a paleontologist at the Canadian Museum of Nature who was not involved in the research. Upland and mountainous regions tend to produce few fossils because erosion wears down rocks in these biomes, Mallon told Live Science. So it's possible nodosaurids lived there, even if there's no fossil record of these armored dinosaurs at these locations.

"The nature of the fossil record is that it's patchy and incomplete," Mallon said. "It's very hard to tell a comprehensive story when you've only got a few pages out of a phone book's worth of time."

It's also not clear from the fossil record why so few nodosaurid species have been found in Asia compared with North America, Zelenitsky said. While several ankylosaurid species have been found further inland in Asia, few nodosaurid fossils have been unearthed on the continent.

"It could be the rock record, or just that [nodosaurids] weren't able to diversify as much in Asia," Zelenitsky said.

In future studies, "I hope that we find more of this animal," Mallon said. "It incites us to keep digging so that we can learn more about this animal and test some of our ideas about just what it is."

Tyrannosaurus rex was a hottie with a body temperature similar to our own, according to a new analysis of their teeth.

The finding supports the idea that T. rex was a fast, energetic predator and scavenger, not an animal that basked in the sun to gain energy like most modern-day reptiles.

T. rex, which lived between about 68 million and 66 million years ago, at the end of the Cretaceous period (143.1 million to 66 million years ago), was one of the largest carnivorous dinosaurs that ever lived.

Previous studies have already suggested that T. rex and its relatives were warm blooded, but now scientists have estimated the dinosaur's body temperature for the first time by studying different isotopes, or forms, of the same chemical elements in the enamel of three T. rex teeth from specimens found in the Hell Creek Formation in Montana.

Rare, heavy isotopes of carbon and oxygen bond together differently in growing tooth enamel depending on the temperature. The number of bonds formed between these rare isotopes is greater at cooler temperatures than it is at warmer temperatures, which means warm-blooded, or endothermic animals, that can regulate their own body temperature, have fewer of these chemical bonds in their teeth than cold-blooded, or ectothermic, animals, which rely on their environment for warmth.

By measuring the bonds in carbon dioxide (CO₂) given off when dissolving small samples from the T. rex teeth, Randon Flores, a geologist at the University of California, Los Angeles (UCLA), and his colleagues could estimate where on the scale of animal body temperatures T. rex sat.

They put the T. rex body temperature at 97.3 degrees Fahrenheit (36.3 degrees Celsius), comparable to that of a human or an elephant. Modern, cold-blooded reptiles tend to have lower body temperatures of about 82-86 F (28-30 C), while most birds — descendants from T. rex's branch of dinosaurs — tend to be much warmer at 104-109 F (40-43 C). Therefore, these findings, published Wednesday (Sept. 16) in the journal Science Advances, show how much this relative of modern birds had already diverged from cold-blooded dinosaurs like Triceratops and Stegosaurus.

"The temperature is about what I would have guessed — higher than a reptile or a slow mammal like a sloth, but lower than an avian," study co-author Robert Eagle, a geobiologist at UCLA, said in a statement.

These findings have implications for how and where the T. rex might have lived. A warm-blooded T. rex would have been an energetic, active animal, chasing or scavenging food to fuel its fast metabolism rather than basking in the sun to gain energy, wrote the authors.

It also means that during the Cretaceous period, one of the warmest periods in Earth’s history, about 11-25 F (6-14 C) warmer than today, T. rex would have been able to survive in most of the North American continent, from what is now Mexico up to chilly climates where cold-blooded reptiles wouldn’t have survived. This helps explain why a tyrannosaur fossil has been found in the Kikak-Tegoseak Quarry in Alaska, although there is no trace of other reptiles like lizards, turtles or crocodiles from that period in the region.

The ability for T. rex to inhabit cooler, high latitudes also aligns with recent evidence that tyrannosaurs crossed the Bering Land Bridge between Asia and North America, write the authors.

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

Paleontologists have identified the first confirmed remains of Diplodocus — "Dippy," for short — outside the western U.S., revealing that the iconic long-necked dinosaur reached what is now Spain roughly 150 million years ago.

The findings show that the enormous sauropod didn't live only in North America, as was long thought. Instead, it may have rambled across a land bridge all the way to Europe, the new study suggests.

The discovery, made at the La Tejería site near the small village of El Castellar in eastern Spain, provides some of the strongest fossil evidence yet that dinosaurs could move between North America and Europe during the Late Jurassic, when the Atlantic Ocean was still in its early stages of opening after the breakup of the supercontinent Pangaea. The researchers published their findings Tuesday (Sept. 15) in the Journal of Vertebrate Paleontology.

"Paleontological studies like this one help us better understand the history of life on Earth, reconstruct ancient ecosystems, and understand how they changed through time," study first author Sergio Sánchez Fenollosa, a doctoral student who studies biodiversity and evolutionary biology at the Joint Paleontology Foundation Teruel-Dinópolis (Dinópolis Foundation), a paleontological research institution, told Live Science via email.

A sauropod in Spain

Dippy is one of the best-known dinosaurs. After its fossils made their grand debut at the Carnegie Museum of Natural History in Pittsburgh in the early 1900s, life-size fossil replicas of the towering herbivore were sent around the world, including to England, France, Spain, Argentina and Russia.

But until now, Diplodocus' Late Jurassic fossils were known only from the Morrison Formation in the western United States ‪—‬ and the latest discovery shows that Dippy wasn't a homebody.

The newly unearthed Diplodocus specimen consists of 14 well-preserved tail vertebrae and several chevrons ‪—‬ bones that helped support blood vessels and muscles within the dinosaur's tail.

Study co-author and managing director of the Dinópolis Foundation, Alberto Cobos, said it was a friend who "thought he had spotted some bones on a mountainside," Cobos told Live Science via email. "That very day, I went to the site near El Castellar (a village in the province of Teruel). Sure enough, we saw a couple of sauropod vertebral centers."

Although only part of the skeleton has been recovered, the bones show a series of characteristics associated with Diplodocus, including large cavities corresponding to where air sacs would have been, along with deep grooves running alongside the underside of the tailbones.

"It was an exciting and continuous process of seeing the pieces of the puzzle gradually fall into place," Sánchez Fenollosa said in a statement. "From the early stages of the osteological study, we noticed strong similarities with several diplodocine sauropods … With each new result, the picture became clearer: we were looking at a Diplodocus."

It's unclear which species of Diplodocus the new specimen is, but like others of its genus, it was a huge dinosaur with an extremely long neck and whip-like tail.

"The Diplodocus from El Castellar was approximately 25 meters [82 feet] long (comparable in size to its North American relatives), making it another of the giant sauropods of the Spanish Jurassic," Cobos said in the statement.

An ancient bridge

Between 195 million and 170 million years ago, the supercontinent Pangaea broke apart as the Atlantic Ocean opened. But the ocean was much narrower than it is today, and the continents were not necessarily as isolated as their modern geography is now.

Evidence indicates that temporary land bridges may have allowed some animals to move between the two regions. The most famous prehistoric land bridge is the Bering Land Bridge that humans used to move between Asia and what is now Alaska. Previous research showed the Bering Land Bridge also existed around 68 million years ago, and it may have allowed an Asian ancestor of Tyrannosaurus rex to trek into North America.

One possible route for Diplodocus into Spain may have been a land bridge that connected what is now Newfoundland with the Iberian Peninsula.

Geological conditions may have allowed dinosaurs like Diplodocus to move between continents, Sánchez Fenollosa told Live Science in an email. "This interpretation is supported not only by the fossil record but also by geological evidence," he said.

The newfound Diplodocus fossils also suggest that the distribution of giant sauropods was more complicated than the fossil record previously indicated.

"More complete specimens will be essential to understand this story in greater detail, particularly to determine which Diplodocus species inhabited Europe: whether it was one already known from North America or a previously unknown species," Sánchez Fenollosa said. "This discovery reminds us that even for such iconic dinosaurs, there are still many unanswered questions about their evolutionary history and biogeography."

An exceptionally well-preserved fossilized molar belonging to an adult Pacific mastodon has surfaced in a nature preserve near San Francisco.

Upon first glance, the ancient tooth looked like an "oddly shaped rock" to geologists who were conducting fieldwork in the area, according to a statement from the Midpeninsula Regional Open Space (Midpen), which runs the preserve. But the find was quickly unmasked as a valuable fossil from the last ice age and was sent to scientists at Stanford University for carbon dating.

"The tooth itself is in immaculate condition," Wayne Thompson, a paleontologist and the CEO of Pacific Paleontology, a consulting firm that carried out a preliminary analysis, said in the statement. "It's the most complete mastodon molar from our area, and the most spectacular mastodon molar that I've ever seen. I had chills and shivers up and down my spine."

Brigid Lynch, a geomorphologist with the California-based hydrology consulting firm Balance Hydrologics, found the molar this summer while surveying a creek bed. "As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this," Lynch said in the statement.

Lynch's team was working on a habitat enhancement project to support the threatened California red-legged frog (Rana draytonii) inside the preserve, which is located on the San Francisco Peninsula in San Mateo County. The fossil was a complete surprise and dates to at least 10,000 years ago, when the Pacific mastodon (Mammut pacificus) is thought to have gone extinct.

The Pacific mastodon was first recognized as a species in 2019. It was closely related to the American mastodon (Mammut americanum). Both elephant-like creatures lived in North America during the Pleistocene epoch (2.6 million to 11,700 years ago), but the Pacific mastodon inhabited regions farther west than its cousin, roaming parts of present-day Mexico, California, Oregon and the northern Rocky Mountains of the western U.S., according to the statement.

Pacific and American mastodon fossils reveal slight differences between the species, including a narrower third molar, thicker hind-leg bones and occasionally absent lower-jaw tusks in the Pacific mastodon, according to the Royal Alberta Museum.

The newfound tooth is "another puzzle in the Ice Age saga that we can put into place," Thompson said. To get a precise date for the fossil, Midpen donated it to Stanford University's Doerr School of Sustainability in July, the Los Angeles Times reported.

Researchers will produce a 3D copy of the molar that Midpen plans to use for public outreach and education, according to the statement.

Despite historical portrayals, the dodo was a relatively intelligent bird that might have spent much of its life in the dark, new research suggests.

Dodos were traditionally portrayed as dumb, bumbling birds. But now, scientists have scanned dodo skulls and found nothing to suggest these birds were stupid. What they did find, however, was that the part of the dodo's brain that's responsible for visual processing was small ‪—‬ comparable to that of some nocturnal birds.

"Our interpretation is that this species was really, really not relying much on sight," study first author Sara Citron, a doctoral candidate in behavior and evolution at the University of Lethbridge in Canada, told Live Science. "And the only situation where you're not relying on sight is when there is no light available."

Dodos were wiped out within a century of humans settling on their island home of Mauritius in 1598. However, it wasn't just hunting that drove them to extinction. The sailors introduced dogs, cats, pigs and rats, which would have likely killed the birds and eaten their eggs. These invasive species wreaked havoc on the dodo's ecosystem and continue to plague Mauritian wildlife to this day.

In the new study, published Aug. 5 in the Zoological Journal of the Linnean Society, researchers found that dodo brains scaled with their body size as would be expected for their group, which is made up of pigeons and doves. In other words, their brains weren't especially small for their size, with no evidence of inferior intelligence compared to their relatives.

This isn't the first time researchers have poured cold water on the stereotypical depiction of dodos. A 2024 study found that dodos were likely fast and powerful, rather than slow and bumbling. The new research also builds on a 2016 study that concluded dodos were likely as smart as modern pigeons, which can solve problems and understand abstract concepts like space and time.

The dumb-dodo myth likely stems from accounts that these birds had no fear of humans and tended to run toward trouble. Sailors figured out that if a dodo was in distress, other dodos would run toward their calls, which meant the sailors could catch even more of the birds.

"Apparently, they would just grab one, let it scream and wait, and all the other dodos would run towards this one to see what was the cause of the distress," Citron said.

This might seem like an incredibly stupid survival strategy, but it's not a failure of dodo evolution. Dodos, like many isolated island animals, evolved in an ecosystem that didn't have any mammalian predators, so they were not equipped to deal with humans or the other animals they brought.

Inside the dodo's brain

To better understand dodo biology, the researchers embarked on an international collaborative effort to study as many CT (computed tomography) scans of dodo heads as they could to deduce the size and shape of their brains, starting with one at the University of Lethbridge.

"As soon as we started looking into it, we realized that the optic lobe, which is the part of the brain that processes visual information in birds, was extremely reduced," Citron said. "And that's typically a very good indication of something completely different in the behavior of a species."

The team compared the dodo scans to those collected on 36 living species of pigeons and doves, as well as the extinct Rodrigues solitaire (Pezophaps solitaria), a close relative of the dodo that lived on Rodrigues Island — east of the Mauritius mainland — and suffered the same fate. Unlike dodos, the solitaire's brain was what researchers would expect from a giant pigeon.

The researchers concluded that the difference in visual processing abilities seen in dodos, along with an enhanced sense of smell, might be evidence for the bird being crepuscular — active during twilight — or nocturnal. There weren't any historical accounts of the dodo being active in the dark, Citron said, but that wasn't surprising. Other than the accounts of sailors using dodo cries as bait, researchers don't have any reliable records of the bird's behavior.

"The most absurd thing is that the dodo is this famous bird," Citron said. "Everyone knows what a dodo is, what it looks like. However, we don't know absolutely anything of its behavior or its ecological niche. If you look at the historical accounts, we have more information about how it tasted."

For now, interpretations of the dodo's behavior remain speculative. However, Citron said she wishes the dodo would stop being portrayed as a "stupid thing that is doomed to go extinct because of how inept it is." She argued that animals on the brink of extinction today, especially when they're not like humans, are also dismissed for the same reason.

"[Endangered animals] are intelligent, they are adapted to their environment for millions of years, and the fact that we are destroying it now doesn't mean that they are stupid or they don't deserve to keep living," she added.

An ichthyosaur fossil found in Australia's outback may preserve a rare snapshot of a prehistoric food chain. Around 100 million years ago, the enormous marine reptile swallowed a flying pterosaur before being attacked by a giant ocean predator, new research suggests.

The fossil set, nicknamed "BOB" or "Bag of Bones," belonged to a 20- to 23-foot-long (6 to 7 meters) ichthyosaur, an animal that belonged to a group of dolphin-shaped marine reptiles that lived alongside the dinosaurs during the Mesozoic era, from about 250 million to 90 million years ago. But in a new study, researchers discovered fragments of a pterosaur's jaw — along with fish and cephalopod remains — preserved inside the animal's body cavity.

The finding is the first confirmed evidence that ichthyosaurs ate pterosaurs, an extinct group of flying reptiles that ruled the ancient skies, according to the new study, published July 28 in the journal Gondwana Research.

The fossils may also hint at the ichthyosaur's violent end. Its skeleton — discovered in 2019 in Queensland's outback — contains shattered bones, missing ribs and large crushing injuries. Researchers think the gruesome wounds may have been inflicted by Kronosaurus queenslandicus, a colossal crocodile-like apex predator that lived 120 million to 100 million years ago in the ancient Eromanga Sea in Australia.

A rare prehistoric meal

Fossilized stomach contents are a rare find because they can be preserved only under very specific conditions.

"Rapid burial after death is essential to prevent decay and scattering of remains," study co-author Matt White, a research associate at the University of New England in Australia, told Live Science in an email. "The animal must have died soon after its last meal so stomach acids don't fully digest the prey."

Researchers used advanced neutron imaging to peer inside BOB's stomach contents without breaking any of the fossilized formations. The scans revealed hidden bones and helped scientists determine that the remains were likely associated with the ichthyosaur's digestive system.

White said that advances in imaging technology are making it possible to uncover evidence that would previously have remained hidden inside fossils.

"Scanning techniques have also improved, which has enabled us to see inside specimens and reveal what they potentially ate," White said. The methods can also reveal "the shape of various organs" and internal bone structures, he added.

The pterosaur remains were found near the front of the ichthyosaur's body cavity rather than in their expected position as digested prey, which White and his colleagues think may be because the ichthyosaur struck the seafloor headfirst shortly after its last meal, shifting some of its stomach contents forward.

"We believe the animal died in the water column — perhaps from a pliosaur (Kronosaurus) attack or natural causes — and then sank," White said. "It impacted the seafloor with its rostrum, and connected soft tissues kept most of the body in sequence."

Reconstructing an ancient ecosystem

The fossil offers a rare glimpse into the food web of the ancient Eromanga Sea, which covered much of central Australia during the early Cretaceous period around 145 million to 100 million years ago.

Although ichthyosaurs are known to have eaten fish and squidlike animals, evidence that they ate pterosaurs, a common predator of the ancient skies, has been elusive. The new fossil suggests that at least some ichthyosaurs may have fed on flying reptiles that landed on the water or died and floated to the surface.

"Such discoveries yield valuable information about trophic interactions and allow us to reconstruct ancient ecosystems in greater detail," White said.

When the famous Chicxulub asteroid struck what is now Mexico's Yucatán Peninsula 66 million years ago, it ended the reign of the nonavian dinosaurs. As ecosystems recovered, small, adaptable mammals rapidly spread into newly vacant niches, evolving new diets, larger bodies and more diverse ways of life until they dominated the land within a few million years.

Now, new evidence suggests that even before the asteroid hit, Earth was already beginning to rot.

A study published May 12 in the journal PNAS found evidence of environmental fungal blooms before and after the Cretaceous-Paleogene (K-Pg) mass extinction event. Looking at microscopic fossils from rocks dating to the K-Pg event in North America, a team of researchers led by Dr. Arturo Casadevall, chair of the Molecular Microbiology and Immunology Department at Johns Hopkins University, identified an earlier fungal bloom dating to roughly 30,000 to 100,000 years before the asteroid hit, during a period of cooling linked to intense volcanic activity in the Deccan Traps in what is now India.

The researchers also found a fungal spike immediately after the Chicxulub impact exactly when dead plants and animals would have littered devastated ecosystems. The finding adds to earlier evidence from New Zealand that suggests the fungal bloom wasn't just a local event.

This idea feeds into a controversial idea called the fungal infection-mammalian selection (FIMS) hypothesis. First proposed two decades ago by Casadevall and subsequently updated in 2018 and 2026 papers, the FIMS hypothesis suggests that the abundance of fungus before the asteroid impact may have helped mammals gain an evolutionary advantage over the dinosaurs that remained after that cataclysm.

The hypothesis doesn't argue that fungus wiped out the dinosaurs. Instead, it proposes that mammals' live births and immune systems may have helped them withstand the rise of fungus in ways egg-laying reptiles and nonavian dinosaurs could not, thereby giving them the upper hand in disrupted ecosystems full of rot, cold, starvation and polluted air.

"The fungal infection mammalian selection hypothesis is focused on how the mammals became the dominant land animals," Casadevall told Live Science via email, "not dinosaur extinction."

But not all experts are convinced. Mary O'Connell, the Chair of the Zoology department at the University of Manchester told Live Science via email that the hypothesis doesn't fit all the evidence and that "it emerges from a chain of plausibility arguments rather than direct evidence, and the links in the chain are weaker than the framing may suggest."

A fungal world before the asteroid

To find this pre-asteroid fungal bloom in their new study, Casadevall and Rosanna Baker, who researches fungus at Johns Hopkins, focused on palynomorphs — tiny fossilized organic remains, including fungal spores, fungal hyphae and plant pollen — preserved in ancient sediment layers from the Denver Basin in Colorado dating back to the K-Pg extinction.

Baker counted between 100 and 500 microfossils per sample across sediment layers spanning about 60,000 years before the K-Pg mass extinction event to 30,000 years after it. Most samples were dominated by plant material, but some layers contained 50% or more fungal spores. The researchers interpreted this high proportion of fungal spores as a sign of ecological disturbance ‪—‬ more dead material and more fungi feeding on it, especially after the dinosaur-killing asteroid.

Baker and Casadevall also found an earlier fungal bloom dating to roughly 10,000 to 30,000 years before the asteroid impact.

"What surprised us was the proliferation in association with Deccan volcanism, which implies ecological disruption prior to [the] meteor impact," Casadevall told Live Science via email.

In other words, ecosystems may have already been under stress — and faced with a fungal overgrowth — before the asteroid delivered the final blow.

The case for FIMS

When Casadevall first proposed the FIMS hypothesis, it rested on a simple observation: Mammals are unusually resistant to invasive fungal diseases.

Fungi are major pathogens of plants, insects, amphibians and many reptiles, but life-threatening systemic fungal infections are relatively rare in mammals with healthy immune systems. Casadevall argued that mammals' relative resistance to fungi came from their sophisticated immune systems. In mammals, first-line, relatively nonspecific defenses such as neutrophils recognize fungal cell walls, engulf spores and attack invasive filaments, while the adaptive arm of the immune system excels at building customized antibodies that selectively target specific fungi, and then creating immune memory so the invaders are recognized the next time they're encountered.

Casadevall also initially believed that mammals' high, stable body temperatures — generally around 97 to 104 degrees Fahrenheit (36 to 40 degrees Celsius) — could prevent many environmental fungi from growing well enough to establish an infection.

"The success of mammals made no sense given their high energy needs and this idea provided a plausible mechanism for their success," Casadevall said.

After the asteroid hit, forests burned, plants died, darkness fell and dead matter piled up, providing a feast for fungi. If fungal spores filled the air, surviving animals may have inhaled enormous, possibly dangerous doses.

However, the FIMS hypothesis proposes that mammals had several possible adaptations against these fungal invaders that other animals did not. In addition to having warm body temperatures and complex immune systems, mammals who could maintain stable body temperatures could forage during the cold "impact winter," ‪when ash and dust blocked out the light of the sun. Meanwhile the dinosaurs, who were originally thought to be the "cold-blooded," would have struggled to stay active and find food, leading them to become weaker and more susceptible to disease.

Differences in gestation may have mattered, too. Many mammals protect developing embryos inside the mother's body, where warmth and immunity could shield them from fungi. In contrast, all dinosaurs laid eggs. Those eggs developed in nests, which were often in contact with soil and decaying plant matter ‪—‬ the exact environments where fungi thrive. Modern fungi can invade reptile eggs, and fossilized hyphae, a type of fungus, was described in dinosaur eggshells in a 2008 study.

That does not prove fungi wiped out dinosaur nests. Fossilized hyphae could suggest either that fungi invaded a living egg, or that fungi colonized the egg after death. Still, eggshells provide one clue that fungi were a problem for the survival of dinosaur young..

A sick sauropod

Another potential line of evidence to buttress the FIMS hypothesis came from dinosaur bones that showed evidence of fungal infection.

In 2022, a team led by Cary Woodruff, curator of vertebrate paleontology at the Phillip and Patricia Frost Museum of Science in Miami, described a Late Jurassic sauropod fossil from Montana with unusual lesions in its neck vertebrae. The dinosaur, an immature diplodocine known as MOR 7029, lived roughly 150 million years ago, long before the asteroid impact.

Sauropods had long, air-filled neck bones connected to their respiratory system. In fossils of healthy sauropods, the places where air-sac tissue met bone are smooth, sometimes glass-like, Woodruff told Live Science.

But in this animal, the normally smooth sockets were rough and irregular. "Coming out of the socket — like imagine coming out towards you —it looked like fossilized heads of broccoli florets," Woodruff said. "And I had never seen that."

Unsure what he was looking at, Woodruff posted a photo online and asked whether anyone had seen anything similar. Other anatomists and paleontologists quickly weighed in. Their response, he recalled, was essentially, "That's exactly what we would have predicted a respiratory infection to look like," he said.

By comparing the fossil lesions with respiratory diseases in modern birds, which are living dinosaurs, the team tentatively flagged the condition as airsacculitis with associated osteomyelitis ‪—‬ air-sac inflammation that had spread to nearby bone.

However, the researchers could not identify the exact disease that caused the inflammation. In modern birds, airsacculitis can be caused by fungal infections such as aspergillosis, but also by bacterial infections. Without preserved soft tissue or fungal structures, they stopped short of confirming a fungal infection diagnosis.

Either way, Woodruff thinks the sauropod was probably sick enough that the infection contributed to its death. It may have become too weak to keep up, too ill to eat or drink properly, or too vulnerable to escape predators.

The case against FIMS

Even so, many experts remain skeptical of Casadevall's hypothesis. For one thing, the asteroid and its aftermath already explain a tremendous amount. The impact triggered tsunamis, earthquakes and a global food-web collapse. Those disasters alone would have killed off large dinosaurs at the top of disrupted food chains.

Another problem revolves around body temperature. In 2005, when Casadevall first proposed his hypothesis, dinosaurs were often thought of as "cold-blooded," while mammals were "warm-blooded." But over the years, research has uncovered that many nonavian dinosaurs, such as Velociraptor, T. rex and Brachiosaurus, were likely warm-blooded, too ‪—‬ so body temperature wouldn't explain why fungus would have been a big problem for many dinosaurs.

Complicating the picture, birds — the only surviving dinosaurs — often have higher body temperatures than mammals do. So the FIMS theory rests on an assumption that living examples of dinosaurs don't support, Flynn said.

Around the time of the asteroid impact, cold-blooded creatures like turtles and crocodilians that lived in the water "don't really suffer as severely as other groups, even including mammals," Andrew Flynn, an assistant professor of paleobotany at New Mexico State University, told Live Science. "Clearly this fungal thing is not probably what's causing mammals to rise up and go on to dominate the ecosystem."

The FIMS hypothesis also has a contradiction at its heart, said Jingmai O'Connor, a paleontologist at the Field Museum in Chicago.

"It's just a hypothesis I had vaguely heard about but was not popular, not often mentioned, and I guess I would say 'out of favor,'" O'Connor told Live Science via email. "If everything we know that suggests dinosaurs are more susceptible to fungal infections is based on living dinosaurs (birds) and they survived, doesn't that rather undermine this hypothesis?"

Dr. Isabel Jimenez, an assistant professor at Johns Hopkins University and a proponent of FIMS, agrees that this discrepancy must be explained.

"For the FIMS hypothesis to still hold water, we have to consider alternative mechanisms by which dinosaurs could have been more susceptible to fungal diseases than mammals," Jimenez told Live Science in an email.

Modern-day birds are avian theropods — the surviving branch of the dinosaur family tree — and likely faced the same fungal pressures as their extinct relatives. More recently, in 2026, Jimenez and Casadevall have suggested a tweak to their theory: that some of the small-bodied, beaked, flying or semiflying theropods may have been able to pull through, despite some baseline higher susceptibility to fungal disease. That's because they were small, had feathers to better insulate their bodies, and maintained generalist diets that enabled them to use more food sources than the dinosaur lineages that died out.

Working with Jimenez, Casadevall outlined an updated version of the FIMS hypothesis in a paper published earlier this year. In it, they propose that dinosaurs' respiratory systems may have made them more at risk than their mammalian counterparts.

Whereas mammals breathe by expanding and contracting flexible lungs filled with blood-rich alveoli, modern birds — and probably many dinosaurs — have rigid lungs ventilated by a network of thin-walled air sacs. The air sacs act as bellows, maintaining one-way airflow through the lungs, but they perform little gas exchange and have relatively poor blood supply. This system could have also carried inhaled fungal spores deep into the respiratory tract, where they may have settled in air sacs that are harder for circulating immune cells to reach and clear.

While birds have a similar sophisticated immune system as mammals — including macrophages and antibodies — their air sacs extend throughout the body and sometimes into the bones, making fungal infections easier to spread beyond just the respiratory system.

This possible weakness is what Jimenez and Casadevall suggest is what made air-sac-bearing dinosaurs vulnerable to fungal infections, similar to modern birds.

After the asteroid strike, there would have been soot and sulfur polluting the air and dinosaurs would have been nutritionally stressed. "So secondary fungal infections are certainly possible," Jimenez said, referring to infections that take root after the body's defenses are weakened.

But skeptics argue that even with these updates in the FIMS hypothesis, more evidence is needed to show it's not just possible but likely.

The idea that their air-sac respiratory systems made them more vulnerable to fungus is "a more testable claim," but its likely impact on dinosaurs would also be more limited, because of competing environmental factors, O'Connell said.

And because only a handful of fungal species actually cause disease in animals, to show that fungi worsened dinosaur deaths, researchers would need to find evidence of elevated fungal disease in dinosaur fossils from right after the asteroid struck, O'Connell said.

"We would also need to be able to identify elevation of pathogenic fungal spores in the sedimentary record at that boundary, rather than just more spores," she said.

Overall, "the fungal infection-mammalian selection hypothesis feels like a conjecture in search of any supporting evidence," paleontologist and science writer Riley Black, told Live Science in an email.

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

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."

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

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

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

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

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

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

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

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

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

Science upended?

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

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

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

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

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

"Onto something big"

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Finding a fossil among the fragments

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

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

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

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

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

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

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

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

The bird hunter

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

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

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

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

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

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!

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.

Scientists have cracked a major mystery about mammal evolution after discovering a 250 million-year-old fossilized egg from before the time of the dinosaurs. Researchers say the specimen, which holds a curled-up embryo of the plant-eating animal Lystrosaurus, is the first known egg ever found from a mammal ancestor, proving that mammals' ancestors laid eggs.

The egg could help paleontologists better understand how these animals survived the Permian-Triassic extinction, also known as the Great Dying, which occurred around 252 million years ago. During this event, Earth faced brutal heat, drought, volcanic eruptions and ocean acidification, and 90% of Earth's species died.

"It reveals how reproductive strategies can shape survival in extreme environments: by producing large, yolk-rich eggs and precocial young, Lystrosaurus was able to thrive in the harsh, unpredictable conditions following the end-Permian mass extinction," Julien Benoit, a paleontologist and associate professor at the University of the Witwatersrand, South Africa's Evolutionary Studies Institute, said in a statement.

The researchers revealed their findings April 9 in the journal PLOS One.

Which came first: the therapsid or the egg?

The fossilized egg was first found in 2008 during fieldwork near the Xhariep municipal district in South Africa. Although the specimen only had small flecks of bone near a nodule, it contained a nearly complete, tightly curled embryo. The researchers identified the animal as Lystrosaurus, an early ancestor of mammals belonging to a group known as therapsids. Therapsids were mammal-like reptiles that lived around 272 million to 250 million years ago that modern mammals descended from.

"The adult [Lystrosaurus] looked like a pig, with naked skin, a beak like a turtle, and two tusks sticking out and pointing down," the researchers wrote for The Conversation.

Scientists have known about this mammal ancestor for years, but they weren't sure whether the animal laid eggs.

Initially, the researchers couldn't determine if the embryo had already been born or was still inside an egg when it died, because the fossil lacked an outer shell and only the embryo was preserved.

"I suspected even then that it had died within the egg, but at the time, we simply didn't have the technology to confirm it," Jennifer Botha, a professor at the University of the Witwatersrand's Evolutionary Studies Institute in South Africa, said in a statement.

For the new study, the researchers used powerful CT scans at the European Synchrotron Radiation Facility in France to study the fossil without damaging it. The scans revealed tiny structures inside the fossil, including an unfused lower jaw, still in two halves. That meant the embryo was not developed enough to feed on its own ‪—‬ a sign that it hadn't hatched yet. The researchers suspect the shell was leathery and dissolved.

"For over 150 years of South African palaeontology, no fossil had ever been conclusively identified as a therapsid egg," Botha said in the statement. "This is the first time we can say, with confidence, that mammal ancestors like Lystrosaurus laid eggs, making it a true milestone in the field."

Putting all the eggs into one surviving basket

The researchers found that Lystrosaurus laid unusually large eggs for its body size. In living animals, large eggs carry more yolk, which can fuel more complete development before they hatch. That finding points to Lystrosaurus having young that were relatively mature and mobile soon after birth, the researchers suggested. This would have made these animals more capable of feeding themselves and avoiding danger, thus helping them survive the Great Dying, the researchers said.

The larger size of the eggs and their leathery texture helped these animals survive in other ways too, the researchers suggested.

"The larger the egg, the smaller its surface area (comparatively speaking), so Lystrosaurus eggs would lose less water through their leathery shell than those of other species of that time," the researchers wrote in The Conversation. "Given the dry environment during and in the immediate aftermath of the extinction, this was a significant advantage, especially since hard-shelled eggs would not evolve for another 50 million years, at least."

While many lineages vanished in the Permian-Triassic extinction event, Lystrosaurus not only survived but became one of the dominant land animals afterward.

"Growing up fast, reproducing young and proliferating were the secrets of Lystrosaurus survival," the researchers added in The Conversation article.

The findings could help scientists understand more about how animals can survive changing climates.

"In a modern context, this work is highly impactful because it offers a deep-time perspective on resilience and adaptability in the face of rapid climate change and ecological crisis," Benoit said in the statement. "Understanding how past organisms survived global upheaval helps scientists better predict how species today might respond to ongoing environmental stress, making this discovery not just a breakthrough in palaeontology, but also highly relevant to current biodiversity and climate challenges."

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

While exploring a cave in central Texas, scientists unearthed a long-lost ice-age ecosystem, including the remains of a giant tortoise and a lion-size armadillo relative, among a trove of fossils in an underground stream.

In a study published March 19 in the journal Quaternary Research, researchers say the cave may preserve the remains of animals that lived during a relatively warm period of the last ice age. If the findings are validated, the site would offer a rare look at an animal community that was missing from central Texas' fossil record.

"It blew my mind," lead author John Moretti, a vertebrate paleontologist in the University of Texas at Austin's Jackson School of Geosciences, told Live Science. "Just the abundance of fossils and the animals those fossils represent were really exciting."

Moretti and John Young, a local caver, were exploring Bender's Cave, near San Antonio, in 2023, when they came across the fossils. The cave is difficult to access and has a subterranean stream running through it, so it had largely been ignored by paleontologists. However, they suspected fossils were present, as amateur cavers had previously brought in their finds, Moretti said.

It was Moretti and Young who found the ice-age fossils simply lying in the mud.

"We have bags attached to our waists, and we're picking up fossils as we go," Moretti said. Over six trips between 2023 and 2024, Moretti and Young discovered fossils from 21 areas in the cave. Among the finds were a claw from a giant sloth (Megalonyx jeffersonii), mammoth teeth, and bones of camelids (Camelops), the long-legged ancient relatives of modern day llamas.

But what really intrigued them was the discovery of fossils of two ice-age beasts: a pampathere (Holmesina septentrionalis), a giant armadillo relative that lived during the middle to late Pleistocene (781,000 to 126,000 years ago) ; and an extinct genus of giant tortoise (Hesperotestudo).

The discovery of these two fossilized animals puzzled Moretti and Young because these ice-age giants were not known to have lived in this area. For more than a century, researchers have studied ice-age fossil sites in central Texas and built a picture of the region during that time as a dry grassland dominated by grazing animals. According to Moretti, this climate would not have been suitable for the tortoise or the pampathere.

Moretti and Young suggested that the animals' remains washed into the cave system from the surface through sinkholes during floods and then settled on the streambed. If this is the case, the animals may have lived during a warmer interglacial period, roughly 100,000 years ago, when temperatures rose and animals that favored milder conditions moved into the region, the researchers proposed.

Moretti said they have not been able to accurately date the bones because the collagen proteins often used as the biomarker in fossils were completely eroded by the mineral-rich water. This water also contaminated many of the fossils, as the bones absorbed carbon and other minerals after being deposited. This means a test may measure this contamination rather than the fossils' true ages.

To overcome this challenge, the team is now trying to date the calcite crusts that formed on the bones after they entered the cave. Although these results won't provide exact dates for the fossils, they can set a minimum age for when they were deposited. With these dates, the researchers hope to narrow down whether the cave fossils represent a warmer interglacial chapter of Texas' history.

"We still don't know everything about the natural world," Moretti said. "There's still a lot to discover out there."

Think you know all about the ice age? Test your smarts with our mammoth quiz!

Paleontologists have revealed a bizarre prehistoric creature with a twisted jaw and sideways-facing teeth, and the water-dwelling weirdo was already a "living fossil" when it existed 275 million years ago.

The newly described species, named Tanyka amnicola, is an archaic member of the tetrapods — a large group of four-limbed vertebrates that today includes reptiles, birds, mammals and amphibians, according to a study published Wednesday (March 4) in the journal Proceedings of the Royal Society B.

Despite predating the dinosaurs, T. amnicola was already an evolutionary relic in its time, during the Permian period. Many of the earliest tetrapod lineages, known as stem tetrapods, had already disappeared by that time. But the lineage that T. amnicola belonged to seems to have persisted, while tetrapods as a group were diversifying.

"Tanyka is from an ancient lineage that we didn't know survived to this time, and it's also just a really strange animal," lead study author Jason Pardo, a research associate at the Field Museum in Chicago, said in a statement. "In the sense that Tanyka was a remaining member of the stem tetrapod lineage, even after newer, more modern tetrapods evolved, Tanyka is a little like a platypus. It was a living fossil in its time."

Researchers identified the new species from nine fossilized lower jawbones, each roughly 6 inches (15 centimeters) long, recovered from a dry riverbed in northeastern Brazil. Although the creature's lower jawbones were distinctive enough for the team to determine the fossils represented a new species, the lack of other fossilized remains means much about the animal remains unknown.

Given what is known about its close relatives, however, T. amnicola might have resembled a salamander with a slightly longer snout. It possibly measured up to around 3 feet (around 91 centimeters) in length, Pardo said. The type of rocks in which the fossils were found also indicate that the creature lived in lake environments and presumably had "aquatic habits," according to the paper.

Analysis of the lower jawbones revealed some intriguing features — principally, that they were twisted so that the creature's teeth pointed outward to the sides, rather than upward as seen in virtually all other tetrapods.

"The jaw has this weird twist that drove us crazy trying to figure it out," Pardo said. "We were scratching our heads over this for years, wondering if it was some kind of deformation. But at this point, we've got nine jaws from this animal, and they all have this twist, including the really, really well-preserved ones. So it's not a deformation, it's just the way the animal was made."

Furthermore, the inner surface of the lower jawbone, which faces the tongue in humans, was rotated upward; it was covered in a "remarkable" set of small, teeth-like structures called denticles that would have formed a grinding surface, according to the study. These features suggest the animal had a "relatively unique way" of feeding, Pardo said.

The authors suspect that T. amnicola was adapted to munching on small invertebrates or, potentially, some plant material. This would be unusual, given the lack of evidence for plant-eating or omnivorous diets in other stem tetrapods, which are thought to have been carnivores, the team said.

When T. amnicola lived, Brazil was part of the supercontinent Gondwana. According to the statement, the discovery provides a window into Gondwana's animals during this period. "Tanyka is telling us about how this community actually worked, how it was structured, and who was eating what," study co-author Ken Angielczyk, a curator of paleomammalogy at the Field Museum, said in the statement.

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?

Our oldest known vertebrate ancestors had four eyes to spot predators — and, my goodness, they were cute.

Rare fossils from China have revealed that the earliest recorded creatures with spines — jawless fish from half a billion years ago — were equipped with two sets of peepers. Researchers have released an adorable reconstruction of one such four-eyed noodle as part of a study that described the two pairs of eyes, which were surprisingly advanced for their time.

"This changes how we think about the early evolution of vertebrates," study co-author Jakob Vinther, an associate professor in macroevolution at the University of Bristol in the U.K., said in a statement. "It turns out our ancestors were visually sophisticated animals navigating a dangerous world."

Humans come from a long line of vertebrates that researchers can trace back to these jawless fish, called myllokunmingids. Most of our relatives have two eyes just as we do, but it seems myllokunmingids needed more.

Myllokunmingids lived 518 million years ago, during the Cambrian period (541 million to 485.4 million years ago). During this time in Earth's history, large predators were beginning to emerge, making the ocean more dangerous for our small, soft-bodied ancestors.

"In that environment having four eyes may have given these animals a wider field of view — important to avoid predators," Vinther said.

Researchers discovered the eyes in exceptionally detailed fossils preserved in the Chengjiang fossil beds in southern China. In two separate species — Haikouichthys ercaicunensis and an unnamed myllokunmingid species — fossils were found to have two larger eyes on both sides of their heads and two smaller eyes in the middle of their heads, according to the study.

Because soft body parts like eyes are rarely preserved in the fossil record, the researchers were fortunate to find the remains of any eyes in the fossils, let alone four. To confirm the existence of the eyes and examine their structure, the team used high-powered microscopes and chemical analysis.

"We started by examining the obvious large eyes to understand their anatomy — and it was a complete surprise to find two smaller, fully functional eyes between them," study lead author Peiyun Cong, a research professor of paleobiology at Yunnan University in China, said in the statement. "Seeing that was incredibly exciting."

The two smaller eyes were circular, with light-absorbing pigments and lenses that could form images, just like the larger eyes, according to the researchers. The team thinks the second pair of eyes represents the ancestral origins of a more primitive eye-like feature in some modern vertebrates and a gland, which, in humans, helps us sleep.

Some living fish, reptiles and amphibians have a parietal eye, or "third eye," on their heads that detects light only. This parietal eye is tied to the pineal gland, which, in humans and most other vertebrates, is located in the brain. The pineal gland produces the hormone melatonin when it's dark, which, in turn, helps us fall asleep. But half a billion years ago, the precursor to this gland was helping myllokunmingids escape predators.

"What we're seeing is that the pineal organs began as image-forming eyes," Cong said. "Only later in evolution did they shrink, lose visual power, and take on their modern role in regulating sleep."

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."

Rock climbers in Italy stumbled across evidence of what appears to be a sea turtle stampede that took place nearly 80 million years ago. Now, new research suggests these ancient marine reptiles were fleeing an earthquake.

The climbers recognized the significance of their find because the grooves in the rock face on Monte Cònero overlooking the Adriatic Sea reminded them of others that had made headlines earlier that year. Those grooves had been found in another part of the same regional park and were attributed to a Cretaceous marine reptile pressing its paddles into the seafloor. They consulted with fellow-climber and geologist, Paolo Sandroni, who got in touch with Alessandro Montanari, director of the Coldigioco Geological Observatory (OGC).

After an investigation into what these grooves might be, researchers revealed their findings in a study published Nov. 19 in the journal Cretaceous Research.

Sandroni and another member of the team climbed back to the area to collect rock samples and document the site using a drone.

Hundreds of these tracks are located on a layer of the Scaglia Rossa limestone in Cònero Regional Park, a formation that has been extensively studied for decades and preserves millions of years of deep sea sedimentation, study co-author Montanari told Live Science.

What is now part of a mountain was once a deep seabed folded over and thrust upward by tectonic forces millions of years ago, he said. Rock samples collected immediately above the tracks and analyzed by the team reveal important clues about the tracks’ location and the story behind them. For example, they suggest the sea turtles lived around 79 million years ago during the Late Cretaceous Period and indicate that the limestone was part of an underwater avalanche of mud triggered by an earthquake.

Abundant seismic activity in this formation is also supported by decades of collective study. Thin sections slides of the rock samples reveal microfossils of organisms that live along the seafloor, suggesting a hundreds-of-meters deep seafloor environment.

Normally, any traces left by animals would be erased by currents at the sea bottom and "worms, clams and [other] benthic organisms," Montanari said. "They basically garden the seafloor," he noted. But an earthquake caused an underwater avalanche within minutes of the tracks being made, preserving them, he said.

The only vertebrates big enough to make these tracks in the Late Cretaceous were marine reptiles such as sea turtles, plesiosaurs and mosasaurs. The latter two are believed to have been largely solitary, but, if ancient sea turtle behavior mirrored that of some of today's species, the researchers said, then it is possible they may have foraged near shore or left the water to lay their eggs. Whatever brought them together, an earthquake caused them all to flee at once, the team suggested in the study, forcing some of the turtles to swim in the water above toward the open sea, and others to scurry away closer to the deeper seafloor. The impending underwater avalanche propelled them even further out of the way.

Michael Benton, professor of vertebrate palaeontology at the University of Bristol in the U.K., who was not involved in the research, said the study clearly shows the geological context, but he questioned which animal made the tracks.

"The tracks are unusual because they seem to show underwater punting, where the two forelimbs enter the sediment together and the animal pushes forward," he told Live Science. Most vertebrates tend to “walk or swim with the limbs out of sequence” rather than putting two limbs down at the same time, he said. "Marine turtles generally have a very efficient swimming mode," he said, “a bit like underwater flying, where the front paddles swing round” similar to a figure eight pattern, which doesn’t appear to match the tracks found. He also questions why they wouldn't simply "leave the sea bed and swim" away.

Montanari said that while the prints would benefit from further research, it is clear, geologically, that there was an underwater avalanche triggered by an earthquake. He said he hopes their work will prompt fossil experts to further study the site.

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.

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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."

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

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

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

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

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

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

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

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

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

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

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

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."

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

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

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

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

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

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

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

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

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

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

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

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

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

A stunning new animation shows saber-toothed cats attacking a herd of woolly mammoths toward the end of the last ice age in the frozen north of North America.

Airing Wednesday (Nov. 26) in an episode of Apple TV's upcoming series "Prehistoric Planet: Ice Age," the clip explores how iconic ice age animals adapted to changes in their environment as the climate began to warm and their snowy world gradually disappeared. In the video, a pack of five scimitar-toothed cats (Homotherium serum) — a now extinct species of saber-tooth cat — ambush a herd of woolly mammoths (Mammuthus primigenius) that includes a tiny calf and a large adult male.

"That whole story is set in the frozen north, sort of Alaska-Yukon," Mike Gunton, executive producer of the upcoming series and creative director of BBC Studios' Natural History Unit in the U.K., told Live Science in an email. "Those creatures both were sort of stars of the Ice Age, hyper-adapted to life in the cold. The story really is about what happens when those two types of animals are finding their world changing."

As the last ice age drew to a close about 11,500 years ago, ice sheets retreated across North America. This drove some species into extinction, as did hunting from humans living in the Americas at the time, reducing the animal populations that scimitar-toothed cats preyed on. "The prey that they would normally feed on are not around as much as they were," Gunton said. "The fortune of that day is that the cats find a herd of mammoths coming into their pack, and they take the opportunity to try and hunt them."

Woolly mammoths also struggled to survive at the end of the last ice age, and the clip shows the herd taking an unusual route across a plain to find new feeding grounds, Gunton said. Exposed — as they are in the clip — the mammoths come under attack. After a nail-biting few seconds where a scimitar-toothed cat leaps onto the male mammoth and hangs off his trunk by the claws, the mammoth overpowers the five cats and scares them off.

Meanwhile, the females and the calf retreat, huddle together and watch the scene unfold. While researchers think that woolly mammoth herds were female-led and males dispersed at a young age, sexually-mature males occasionally joined herds to mate, Gunton said.

"These males have what they call [musth] — they have these glands on the temporal area of their skulls, and they weep, producing particular pheromones — and that gets everybody excited," he said. "This mammoth was with them [in the clip] because you get males coming to join a herd with the idea of mating with the females, and they will spend a lot of time wandering around with them."

The mammoths survive this encounter, but the scimitar-toothed cats eventually triumph in a sequence later in the show, Gunton said.

"At the end of the program, we see them trying again with [a] different strategy," he said, adding that one of the cats lunges off a high rocky outcrop onto the back of the male mammoth, giving the other cats the opportunity to pile on and take the mammoth down. "And then they feed," Gunton said.

The hunting technique of scimitar-toothed cats in the second clip is similar to that of leopards, which also leap onto their prey from above, Gunton said. Recreating these attacks was a big challenge for the filmmakers, because "you've got two animals created in visual effects actually interacting with each other," he said.

A bigger challenge still was making the animals appear realistic, given that they are covered in fur and moving in a snowy landscape.

"Every one of those creatures will have millions of individual little hairs on it, all of which behave on their own independently," Gunton said. "Then they're doing stuff in snow, so you've got complex interactions between snow itself. It's sort of the pinnacle of what is tough to do in this series."

Read more | How to watch 'Prehistoric Planet' – Streaming details as new season 'Ice Age' lands on Apple TV

For the first time, scientists have successfully sequenced woolly mammoth RNA, shattering the assumption that this fragile genetic molecule couldn't survive from so long ago.

RNA, or ribonucleic acid, carries instructions between DNA and an organism's protein-building machinery, acting as a messenger to turn genetic information into proteins. RNA can reveal which genes are active in a cell at a given moment, as well as how gene-activity patterns within a cell change over time. Thus, ancient RNA can inform scientists about the cellular states of extinct species.

Although the technology behind ancient DNA research has surged over the past 20 years, ancient RNA research has seen few successes. This is due in part to its construction, as DNA molecules are double-stranded and therefore sturdier than the single-stranded RNA.

While DNA offers the blueprint of an organism, there are limits to the information it reveals. RNA "opens a window into how" that blueprint is implemented within each cell of the organism, said study co-author Zoé Pochon, a doctoral student at Stockholm University.

The aptly-named messenger RNA (mRNA) "is DNA's messenger," she told Live Science in an email. "In other words, it carries working copies of DNA instructions from the nucleus to the cell." Other parts of the cell then follow these instructions, she added.

In the new study, published Friday (Nov. 14) in the journal Cell, the researchers turned to 10 well-preserved woolly mammoth (Mammuthus primigenus) specimens from Siberia that dated to 10,000 to 50,000 years. The team hoped that the frozen conditions had preserved more of the specimens and so would produce better results.

One specimen in particular — Yuka, a ginger-colored juvenile mammoth — yielded spectacular results. Yuka is about 39,000 years old, making this the oldest RNA sequenced to date. Previously, that distinction was held by tissues sampled from a canid dated to approximately 14,300 years.

Remarkably, the scientists found definite genetic signals that Yuka, previously believed to be a female based on its physical attributes, is actually a male.

Additionally, the RNA offered insights into Yuka's muscle function — specifically, the RNA "creating the proteins that are stretching and contracting the muscles," said study lead author Emilio Mármol Sánchez, who was working at the Center for Evolutionary Hologenomics, University of Copenhagen at the time of the paper. The team "also found a whole set of regulatory genes,' he told Live Science.

When cells die, what is left behind is the last function of the RNA. "What we are capturing here is, in a sense, a snapshot of the last moments of the life of these mammoths" within their cells, Mármol Sánchez said.

What the team saw in Yuka's muscle RNA reflects the potential horror of its last moments. Mármol Sánchez explained that they uncovered "molecular evidence of metabolic cell stress in Yuka's muscle," which corresponds with what a separate scientific team described in 2021. In that study, the researchers noted many claw marks that may have been made by cave lions (Panthera spelaea), as well as bite marks from smaller predators on the mammoth's body and tail. But whether Yuka was hunted and killed by large predators or simply scavenged after death is unknown. The researchers do not know what caused the cell stress observed in the RNA.

Federico Sánchez Quinto, a paleogenomicist at the National Autonomous University of Mexico's (UNAM) International Laboratory for Human Genome Research who was not involved in the research, considers this "a breakthrough publication in the field of paleogenomics." He described the study as "fascinating since it accomplishes something that had been previously unimaginable, as RNA is extremely unstable even in favorable conditions." Moreover, "this study obtains RNA from an older sample [than other recent RNA work], in larger amounts and with more certainty," he told Live Science in an email.

The findings have revealed that it's possible to extract RNA from extremely old specimens and showcases a new area of potential study for other researchers, the team said. In addition, the team has included a roadmap to help others successfully obtain ancient RNA.

"Being able to recover RNA from ancient samples, in addition to DNA, is like opening a new window into the biology of extinct animals," study co-author Love Dalén, professor of evolutionary genetics at the Centre for Palaeogenetics at Stockholm University, told Live Science. "It's yet another powerful tool that lets us see which genes were active in different cell types, which ultimately can help us better understand which genes made a mammoth a mammoth!”

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

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

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

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

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

Whale of a pig

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

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

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

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

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

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

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

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

Researchers have unearthed a giant "warrior" lizard that stalked Brazil 240 million years ago in the Triassic period, just before the dawn of the dinosaurs. The discovery fills in gaps in our understanding of the time before the dinosaurs dominated Earth, and further highlights the links between what is now Africa and South America.

The armor-plated reptile resembles a dinosaur but is actually an ancestor of modern crocodiles. Scientists have called the creature Tainrakuasuchus bellator, which is a mixture of Greek, Latin and Indigenous Brazilian language Guarani, meaning "pointed-tooth warrior crocodile." The team revealed its findings in a study published in the Journal of Systematic Palaeontology on Nov. 13.

"Its discovery helps illuminate a key moment in the history of life, the period that preceded the rise of the dinosaurs," study lead author Rodrigo Temp Müller, a paleontologist at the Federal University of Santa Maria in Brazil, said in a statement.

During the Triassic (252 million to 201 million years ago), Archosaurs dominated the world of land-based vertebrates — the name means "ruling reptiles" — and is split into two main groups. One group, Ornithosuchia, evolved into birds and dinosaurs, while the other, Pseudosuchia, gave rise to crocodilians, such as modern crocodiles.

T. bellator belongs to Pseudosuchia. It was about 7.9 feet (2.4 meters) long and weighed 130 pounds (60 kilograms). It had a long neck and thin jaw full of sharp teeth. Very few of these types of Pseudosuchia (called poposauroids) have been found in South America, the researchers noted.

The team found the partial skeleton of T. bellator, including the lower jaw, backbone and pelvis, during an excavation in May in the Dona Francisca municipality in Brazil.

The reptile's back was covered in bony plates called osteoderms, which modern crocodiles also have.

"This animal was an active predator, but despite its relatively large size, it was far from the largest hunter of its time, with the same ecosystem home to giants as big as seven meters [23 feet] long," said Müller, who led the team of palaeontologists that excavated T. bellator. "Despite the diversity of pseudosuchians, they remain poorly understood." Fossils of some of their lineages, such as poposauroids, are "extremely rare" in the fossil record, he said.

T. bellator is closely related to another individual discovered in Tanzania, he said. Mandasuchus tanyauchen, discovered in 1933, lived about 245 million years ago, when Africa and South America were both part of the supercontinent Pangea.

"At that time, the continents were still united, which allowed the free dispersal of organisms across regions that are now separated by oceans," Müller said. "As a result, the faunas of Brazil and Africa shared several common elements, reflecting an intertwined evolutionary and ecological history."

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

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

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

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

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

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

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

Interpreting the drag mark

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

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

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

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

Old dung and urine

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The case for Nanotyrannus

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

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

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

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

Paleontologists respond

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

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

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

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

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

Is Jane a new species?

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

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

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

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

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

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

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

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

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

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

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

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

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

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."

A nearly complete fossil skeleton found on the U.K.'s Jurassic Coast represents a newly identified species of ancient marine reptile that lived alongside dinosaurs.

The ichthyosaur, dubbed Xiphodracon goldencapsis, was likely around 10 feet (3 meters) long when it lived, according to a study published Friday (Oct. 10) in the journal Papers in Palaeontology. It had large eye sockets and a long, narrow snout shaped like a sword.

The specimen dates to a period in the Early Jurassic known as the Pliensbachian, which lasted from about 193 million to 184 million years ago. By studying an ichthyosaur fossil from this period, scientists could learn more about a critical point in these aquatic animals' evolution, according to the study.

Fossil collector Chris Moore found the remains in 2001 along the Jurassic Coast, a 96-mile (154 kilometers) stretch of seaboard in Dorset known for being a treasure trove of fossils.

Moore sold the fossil to the Royal Ontario Museum in Canada shortly thereafter. Although it was identified as an ichthyosaur, it wasn't studied in detail until recently.

"I remember seeing the skeleton for the first time in 2016," study co-author Dean Lomax, a paleontologist at the University of Manchester and the University of Bristol, said in a statement. "Back then, I knew it was unusual, but I did not expect it to play such a pivotal role in helping to fill a gap in our understanding of a complex faunal turnover during the Pliensbachian."

The new genus name, Xiphodracon, comes from the Greek words "xiphos," meaning sword, and "dracon," meaning dragon — a reference to ichthyosaurs' "sea dragons" nickname. Its species name, "goldencapsis," comes from Golden Cap, the site on the Jurassic Coast where the ichthyosaur was found.

The fossil also hints at how the individual ichthyosaur lived and died.

"The limb bones and teeth are malformed in such a way that points to serious injury or disease while the animal was still alive, and the skull appears to have been bitten by a large predator — likely another much larger species of ichthyosaur — giving us a cause of death for this individual," study co-author Erin Maxwell, curator of fossil aquatic vertebrates at the State Museum of Natural History Stuttgart in Germany, said in the statement. "Life in the Mesozoic oceans was a dangerous prospect."

X. goldencapsis could also help to clarify a major shift in ichthyosaur speciation in the early Jurassic. Although scientists have found many ichthyosaur fossils from before and after the Pliensbachian, the two groups have very few species in common, suggesting a major turnover sometime during the Pliensbachian. In fact, ichthyosaur fossils from the Pliensbachian period are rare.

The newly discovered ichthyosaur "is more closely related to species in the later Early Jurassic … and its discovery helps pinpoint when the faunal turnover occurred, being much earlier than expected," Lomax said. In other words, the shift likely occurred in the early Pliensbachian. However, scientists don't yet know what caused this upheaval.

For now, the X. goldencapsis fossil will be displayed at the Royal Ontario Museum.

The fossilized skeleton of a Jurassic reptile that appears to be part lizard, part snake, has been unearthed on Scotland's Isle of Skye.

This mysterious lizard had hooked, snake-like teeth for hunting down prey 167 million years ago, a new study has found.

The newly discovered species is named Breugnathair elgolensis, which means "false snake of Elgol," honoring the creature's confusing anatomy and the Elgol area of southern Skye, where the fossil was found, according to the study published Wednesday (Oct.1) in the journal Nature.

B. elgolensis was only about 16 inches (41 centimeters) long, but that still made it one of the largest lizards in its ecosystem, according to a statement released by the researchers. Scientists suspect that it hunted smaller lizards, early mammals and even young dinosaurs, such as small herbivorous heterodontosaurids and predatory bird-like paravians.

It had a snake-like jaw and curved teeth similar to a modern python, but its body was short, with fully formed limbs like a lizard. B. elgolensis also had gecko-like features on some of its bones, including the back of its skull. Researchers are still deciphering B. elgolensis' evolutionary history, but its discovery could change the way they look at early snake evolution.

Related: Night lizards survived dinosaur-killing asteroid strike, despite being close enough to see it happen

Scientists currently have a scattered understanding of early lizard and snake evolution. Both animals belong to a group called Squamata, which emerged about 190 million years ago. There's some overlap between members of the group, but lizards came first and generally have four limbs, while snakes are limbless.

"The Jurassic fossil deposits on the Isle of Skye are of world importance for our understanding of the early evolution of many living groups, including lizards, which were beginning their diversification at around this time," study co-lead author Susan Evans, a professor of vertebrate morphology and paleontology at the University College London, said in the statement.

Study co-author Stig Walsh, a senior curator of vertebrate paleobiology at the National Museums Scotland, first uncovered the B. elgolensis fossil in 2015. The team has since spent nearly a decade preparing and studying the specimen, which has included subjecting it to high-powered X-rays and detailed computed tomography (CT) imaging scans.

The researchers determined that B. elgolensis belonged to a Squamata sub-group called Parviraptoridae, which was previously only known from fragments of other fossils. While snake-like bones had been found in close proximity to gecko-like bones, some scientists had assumed they came from two separate animals. The new fossil confirms that one species did indeed have both features, according to the statement.

"I first described parviraptorids some 30 years ago based on more fragmentary material, so it's a bit like finding the top of the jigsaw box many years after you puzzled out the original picture from a handful of pieces," Evans said. "The mosaic of primitive and specialized features we find in parviraptorids, as demonstrated by this new specimen, is an important reminder that evolutionary paths can be unpredictable."

The researchers still aren't sure whether snakes evolved from species like B. elgolensis or whether snakes independently evolved similar mouth parts. It's also possible that B. elgolensis is a stem lineage within Squamata, helping to give rise to all lizards and snakes.

"This fossil gets us quite far, but it doesn't get us all of the way," study lead author Roger Benson, the Macaulay Curator at the American Museum of Natural History's Division of Paleontology, said in the statement. "However, it makes us even more excited about the possibility of figuring out where snakes come from."

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

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

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

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

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

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

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

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

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

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

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

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

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.

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."