Scientists have identified enormous finned "kraken" octopuses that may have reached up to 62 feet (19 meters) long. The behemoths prowled the oceans during the Cretaceous and could be the largest invertebrates ever discovered.

Fossil jaws revealed distinctive markings that suggest these kraken-like octopuses used their powerful jaws to crush hard-shelled prey. That, combined with their gigantic size and evidence of intelligence, put them top of the marine food chain, according to a study published Thursday (April 23) in the journal Science.

This finding suggests scientists need to rethink the oceanic pecking order during the Cretaceous period (145 million years to 66 million years ago).

"These findings revise the view of the Cretaceous ocean as a world dominated only by large vertebrate predators," study co-author Yasuhiro Iba, a paleontologist at Hokkaido University in Japan, told Live Science in an email. "They show that giant invertebrates — octopuses — also occupied the top of the food web."

Other experts say these size estimates are the upper end of a large possible range. Even so, the discovery raises questions about the oceanic landscape of the Cretaceous, such as how these species could grow so large, and whether even larger marine species existed after the Cretaceous period, they said.

Hunting down the apex predators

Species at the top of the food chain shape ecosystems, with their prey responding by evolving protection measures, such as hard shells. Understanding which species held the apex position is essential for understanding how Cretaceous marine ecosystems functioned, Iba said.

Until now, the top dogs were all assumed to be vertebrates, such as mosasaurs and plesiosaurs. However, the lack of preserved evidence from soft-bodied octopuses has made their position in the Cretaceous food chain a complete mystery, the authors wrote in the study.

"Octopuses are known today as highly intelligent animals, but they are extremely difficult to study in deep time because they lack hard external shells," Iba said. "A major motivation for this study was to reveal this almost invisible history of octopuses."

For the study, the researchers reassessed 15 fossilized octopus jaws previously unearthed in Japan and Vancouver Island. They also discovered 12 new Cretaceous fossil octopus jaws in Japan using state-of-the-art digital fossil-mining technology. Combined, these revealed two species of extinct finned octopuses: Nanaimoteuthis jeletzkyi and Nanaimoteuthis haggarti.

The N. jeletzkyi fossils were unearthed in rocks dating to between 100 million and 72 million years ago, pushing back the oldest known octopuses by around 5 million years, and finned octopuses by 15 million years, the authors wrote in the study.

The team then compared the size, shape and wear marks on all 27 jaws with modern-day octopuses to reconstruct their body size, feeding behavior and position in the food web.

The size of living octopuses' mantles — the bulging organ sac sitting above their eyes — is related to the length of their jaws. The total length of living long-bodied finned octopuses is around 4.2 times their mantle length.

Iba and his colleagues used this to estimate just how bulbous N. jeletzkyi and N. haggarti mantles were. From there, they could calculate their possible total length of the long-dead creatures.

Based on the largest jaw for each species, the team estimated the maximum length of N. jeletzkyi was around 10 feet to 26 feet (3 m to 8 m), while N. haggarti was approximately 23 feet to 62 feet (7 m to 19 m). This makes N. haggarti potentially the largest invertebrate discovered to date, and "among the largest body sizes of all organisms in the Cretaceous oceans," the authors wrote in the study. (Modern-day giant squid, Architeuthis dux, reach around 40 feet (12 m) long, and Cretaceous mosasaurs reached approximately 56 feet (17 m) long.)

The kraken jaws also showed signs of intensive wear, with patterns indicating that these animals were dismantling hard-shelled prey using their whole jaws. The front tips on both species' jaws were ground down on one side by as much as 10% of their total size, based on reconstructions. This lopsided loss suggests lateralized behavior, which is linked to being brainier, the authors said in the study.

"These were not just giant octopuses, but giant, intelligent, and highly formidable marine predators," Iba said.

However, while experts applauded the digital fossil-hunting techniques used in the study, they questioned the size estimates of each species.

The study researchers estimated the size of N. jeletzkyi and N. haggarti using "error prone" averages of jaw-to-mantle and mantle-to-total-body size relationships of living species, meaning their results produced a large possible size range for both species, René Hoffman, a paleontologist focusing on fossil cephalopods at the Ruhr University Bochum in Germany, told Live Science in an email.

Their enormous size also does not necessarily mean that these invertebrates were the top predator, Hoffman added.

Christian Klug, a professor of paleontology and expert in cephalopod evolution at the University of Zurich in Switzerland, agreed. While the estimates are within the range of what is possible, he said that some uncertainty is inevitable. "There is no doubt that Nanaimoteuthis was a huge and efficient predator," he told Live Science in an email, but only focusing on the maximum total size "lets one forget that it is conceivable that they may have not reached ten meters."

Are you a sucker for cephalopod science? Test your knowledge with our Octopus quiz!

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.

For the first time, researchers have discovered a piece of fossilized resin, or amber, in Antarctica. The tiny golden fragment, unearthed beneath the seafloor, contains microscopic remnants of an ancient dinosaur-era rainforest that sprawled across the continent 90 million years ago, a new study reveals.

Amber is fossilized resin, or tree sap, that can trap plants, insects, small animals or other organic matter with it as it hardens. The golden-yellow casing is airtight and mostly see-through, meaning it both perfectly preserves and displays whatever is inside it, like a transparent time capsule.

Until now, amber fossils had been found on every one of Earth's continents, except for Antarctica. But in the new study, published Tuesday (Nov. 12) in the journal Antarctic Science, researchers identified a tiny piece of amber, around 0.002 inch (70 micrometers) across, in sediment cores collected beneath the seafloor at a depth of around 3,100 feet (950 meters) off the coast of Pine Island Glacier on Antarctica's west coast.

The tiny fragment dates back to around 90 million years ago during the Cretaceous period (145 million to 66 million years ago). At this time, large parts of Antarctica were covered by a temperate rainforest, similar to those found in New Zealand today, that thrived in warmer climatic conditions — and a tiny part of that lost ecosystem is trapped within the amber.

"This discovery allows a journey to the past in yet another more direct way," study lead author Johann Klages, a sedimentologist at the Alfred Wegener Institute in Germany, said in a statement. "Our goal now is to learn more about the forest ecosystem."

Related: Wildfires burned Antarctica 75 million years ago, charcoal remnants reveal

The sediment cores used in the study were first collected in 2017 and were later revealed to contain fossils of roots, pollen, spores and other remains from flowering plants, which represent some of the best evidence of Antarctica's Cretaceous-era rainforest.

The amber fragment was only recently discovered as researchers broke up the remaining materials into thousands of tiny pieces and painstakingly scanned each one using fluorescent microscopy. Further analysis revealed that it contained "micro-inclusions" from bark that would have likely once lined a conifer-like tree that lived in the ancient forest.

The bark also shows some signs of "pathological resin flow" — a strategy used by trees to seal up damage done to their woody shielding by parasites or wildfires, by creating a chemical and physical barrier with resin.

While the new fragment is small, it is unusually well-preserved despite it being buried under the seafloor.

"Considering its solid, transparent and translucent particles, the amber is of high quality," study co-author Henny Gerschel, a consultant at the Saxony State Office for the Environment, Agriculture and Geology in Dresden, Germany, said in the statement. The fragment must have spent most of the last 90 million years near the seafloor's surface, "as amber would [normally] dissipate under increasing thermal stress and burial depth," she added.

The researchers believe that their findings could open the door to finding more Antarctic amber, which could unlock even more secrets about this ancient rainforest and the dinosaurs that lived in it.

"Our discovery is another piece of the puzzle," Gerschel said.

A newly described duck-billed dinosaur unearthed in Mexico has an epic schnoz to rival that of Yoshi from Super Mario World. 

The dino, named Coahuilasaurus lipani after the region where it was found and the Lipani Apache tribe that lives there, also has unique tooth-like spikes jutting from the roof of its mouth. These spikes that may have been used to eat rough and woody plants in tropical forests 73 million years ago. 

Paleontologists first unearthed the partial skull of C. lipani in the 1980s in the Parras Basin but previously described it as another genus. In the new study, published Sept. 1 in the journal Diversity, researchers took a second look at the fossil, which had been housed in the collections at the National Autonomous University of Mexico since its discovery. Newer analysis techniques allowed them to reclassify the fossil. Claudia Serrano, lead author of the study and paleontologist at Benemérita Escuela Normal de Coahuila, was present during the first description of the specimen in 2006. "When we started working on the material again, we decided 'no, this is different,'" Serrano told Live Science. "We have become much better at describing these things."

Related: Rare fossils reveal basketball-like skin on duck-billed dinosaur

While the partial skull consists only of the dinosaur's snout, this section of the skull is useful in identifying the differences between species, similar to how a bird's beak can reveal a lot about the bird as a whole. The sharp angle of the dinosaur's snout was key to differentiating C. lipani from other species. The scientists also found the distinct tooth-like protrusions projecting from the roof of the mouth,  which hadn't been emphasized in the previous analysis. 

These protrusions may mean that C. lipani was specialized to eat tough plants like palms that flourished in the tropical conditions of the late Cretaceous period when the big-nosed dino lived, around 73 million years ago. Duck-billed dinosaurs, also known as the "cows of the Cretaceous," would have roamed the forests of Mexico at a time when sea levels were higher and temperatures were warmer, according to a statement. Serrano estimates they would have been around 26 feet (8 meters) long, or about the size of two sedans. 

This discovery adds to a growing list of dinosaurs that are unique to Mexico, Serrano said. Discoveries like that of C. lipani and other Mexico-specific species have started to overthrow the assumption that dinosaur species were wide-ranging, the study authors wrote in their paper. Large animals usually have large ranges — that goes for the bison that used to roam from Canada down to Mexico. But instead, individual dinosaur species appear to have had relatively small ranges. Differences in climate, geographical barriers, or perhaps something about the way dinosaurs reproduce may have contributed to their small ranges, but paleontologists still don't quite understand why they stuck to one area, Serrano noted.

A newly identified dinosaur had a squished, pug-like face and teeny arms, but that didn't stop it from gobbling up prey during the late Cretaceous, a new study has found. 

The 16-foot-long (5 meters) predator, named Koleken inakayal, was one of the top predators in what is now Argentina. 

Researchers unearthed K. inakayali fossils in the La Colonia Formation of central Patagonia, according to a study published May 21 in the journal Cladistics. K. inakayali belonged to the Abelisauridae family, which ruled the great southern landmass of Gondwana during the Cretaceous period (145 million to 66 million years ago). 

"These guys were the apex predator in that part of the world," study co-author Michael Pittman, a paleontologist at The Chinese University of Hong Kong, told Live Science. "They were occupying the same role that T. rex would have been doing in parts of ancient North America."

Related: Why did T. rex have such tiny arms?

Abelisaurids like K. inakayali had a similar — albeit smaller — body plan to a T. rex — with bulky hind limbs and stunted arms. However, the skull of the new species was much flatter than those of its relatives. "If it was a dog, it would be a pug," Pittman said. 

Pittman and his colleagues came across K. inakayali fossils sticking out of the remote Patagonian desert in 2015 and excavated them over several years. The team recovered a partial skeleton of a single individual, which included skull bones, tail bones and near-complete legs, according to a statement released by the National Geographic Society, which helped fund the research. 

K. inakayali lived alongside another abelisaurid, Carnotaurus sastrei, which was discovered in the same geological formation in 1985 and is notable for its horns.     

K. inakayali lacked horns, one of several features researchers used to distinguish its skeleton from C. sastrei and other abelisaurids. The newfound species was also smaller than C. sastrei, which had a body length of 26 feet (8 m), according to the Natural History Museum in London. 

The team determined that K. inakayali belonged in its own group within the Abelisauridae family tree. Its genus name, "Koleken," comes from a word in the Teushen language spoken by the native population of central Patagonia. The original Teushen word, "Kóleken," means "coming from clay and water," which the researchers chose because the fossils were in claystone-dominated rocks from an estuarine environment, according to the study. 

The species name, "inakayali," is named after Inakayal, a leader of the Tehuelche native people who fought against the Argentinian military in the 19th century. "He [Inakayal] is known for his resistance against Argentina's Conquest of the Desert military campaign, which resulted in the decimation and displacement of native communities from Patagonia," the authors wrote in the study. 

After identifying K. inakayali, the team looked at abelisaurid evolution, and the rate at which their bodies changed over time compared to other dinosaurs. The researchers found that abelisaurids had rapid skull evolution, which likely contributed to their success. 

"One of the key ingredients for their success was they very rapidly changed their skull configuration, and that opened up new opportunities for them," Pittman said. 

A newly discovered 98-foot-long dinosaur named after the Hindu god Shiva "The Destroyer" stomped around Argentina alongside other long-necked "megatitanosaurs" more than 90 million years ago, scientists reveal. 

Researchers described the humongous beast, called Bustingorrytitan shiva, late last year from fossils discovered in western Argentina. Now, they've worked with an artist to recreate the Cretaceous titanosaur, a stockier type of long-necked sauropod, in stunning images and videos.

B. shiva is among the largest sauropods ever recorded, with an estimated weight of around 74 tons (67 metric tons), according to a study published Dec. 18, 2023, in the journal Acta Palaeontologica Polonica. It wasn't the largest dinosaur — fellow titanosaur Argentinosaurus is one contender for that disputed honor, with an estimated weight starting at 77 tons (70 metric tons) — but B. shiva was still an almighty member of the ancient Argentinian ecosystem. 

The B. shiva discovery in the North Patagonia region of southern South America demonstrates that "megatitanosaurs" with gigantism in excess of 55 tons (50 metric tons) evolved separately within titanosaurs, according to study lead author María Edith Simón, a paleontologist who ran the B. shiva excavation. 

"In Patagonia, we are still at a stage where we are more likely to find something new than something known, and the unknown is often wonderful," Simón told Live Science in an email. "In the publication we reported on a sauropod that became a giant, independently of others within their group."

Related: Gargantuan 'star lizard' was one of the last (and largest) dinosaurs of its kind

A farmer named Manuel Bustingorry found the first giant fossil from B. shiva on his land in Neuquén Province in 2000. Simón said she was responsible for the lab and research area at the nearby Ernesto Bachmann Paleontological Museum in the early 2000s and excavated the farm in 2001.

"When we arrived at the site, it was really exciting," Simón said. "The bone was broken, but it looked like a tibia."

The exposed leg bone was just the beginning. Researchers found the remains of at least four individual dinosaurs belonging to the newfound species, including a relatively complete skeleton and three other incomplete specimens, according to the study.

B. shiva came from the 93 million to 96 million-year-old Huincul Formation of rocks, where Argentinosaurus was found. However, the bones had characteristics that don't match up with known sauropod species, including uniquely shaped crests on the humerus and femur. 

The new research suggests that at least two lineages of gigantic titanosaurs — B. shiva's saltasauroids and Argentinosaurus' lognkosaurs — coexisted in North Patagonia in the middle of the Cretaceous period (145 million to 66 million years ago) alongside smaller sauropods, according to the study.

"Ecologically, each of the sauropods were distinct from one another, with different teeth, heads and bodies," Simón said. "This shows that they were all able to find a form where they could live without competing with one another."

B. shiva's genus name, "Bustingorrytitan," combines the last name of farmer Manuel Bustingorry with "titan," after the giants from Greek mythology. It lived during a period of extinction and new life, so Simón said the team chose the species name "shiva" to reference the supreme deity of Shaivism, who destroys and transforms the universe.  

A turnover event in the middle of the Cretaceous saw the extinction of species such as early diplodocoid sauropods and certain titanosaurs, according to the study. Researchers still have much to learn about what happened to B. shiva, but the study authors noted that some of its saltasauroid lineage survived the turnover and lived on until near the end of the Cretaceous, when the asteroid struck and wiped out non-avian dinosaurs for good. 

Scientists are planting "living fossil" trees in secret locations in a bid to bring back the lost species from the brink of extinction — an effort that could take centuries. 

Wollemi pines (Wollemia nobilis) were believed to have disappeared some 2 million years ago. Fossils of the species dating the Cretaceous period (145 million to 66 million years ago) show they have barely changed in appearance since this time. 

But in 1994, hikers in Australia's Blue Mountains stumbled upon a relict stand of these ancient conifers. Now, only around 60 of them remain in Wollemi National Park. They are threatened by Phytophthora cinnamomi, a pathogenic water mold that causes dieback, and by rampant wildfires that intermittently rage through this region of New South Wales.

Since its rediscovery, wollemi pines have been grown in botanical gardens and private spaces around the world. And the Wollemi Pine Recovery Team, a partnership between Australian government scientists and conservationists, has begun the process of reintroducing seedlings to three sites in Wollemi National Park.

Related: Living fossils — 12 creatures that look the same now as they did millions of years ago

"The sites comprise high-elevation sandstone gorges that are sufficiently deep, narrow and steep-sided to provide refugia from frequent, intense wildfires and drought," representatives said in a statement emailed to Live Science. "There was no evidence of infection with pathogenic Phytophthora species at either site when surveyed immediately prior to the translocations, and there is a low (but non-zero) likelihood of unauthorized visitation due to their remoteness."

Following a pilot transplantation effort in 2012, the recovery team initiated a more intensive project in 2019. Over 400 saplings were transplanted at two sites and — due to drought conditions — the team later hauled several thousand gallons of water to the plants in order to help them survive. Later that year, a substantial number of the trees were destroyed by bushfires. Only 58 saplings made it to 2023.

In 2021, 502 more Wollemi pines were planted at the sites to replace those lost in the fires. "Survival has greatly exceeded expectations, due in part to several years of favorable La Niña conditions following the 2021 population augmentations," the researchers said. La Niña is a periodic climate pattern that features colder-than-average waters in the central and east-central equatorial Pacific. Increased rainfalls due to the climatic phenomenon benefited the new transplants—but that seems to be coming to an end. Landslides caused by heavy rains in 2022 led to further fatalities but more than 80% survived. More will be planted in 2024.

The team has taken extensive steps to prevent introduction of Phytophthora to the sites. Their locations are concealed from the public and even the reintroduction team limits their time near the plants. They repeatedly disinfect their shoes to reduce the likelihood they will track in traces of the water mold. Even a few spores might spell death for this nascent population.

They have also intentionally located some of the young trees in areas that might be subject to bushfires "to help address knowledge gaps regarding their response and ability to tolerate fire," the team said.

While the new populations are being intensively monitored, the fate of the species in the wild is far from assured. The young trees grow less than 0.4 inches (1 centimeter) a year, so it will take decades for them to reach maturity and produce seeds. Some may produce offshoots in the meantime, though when they may begin propagating themselves in this fashion remains unknown. 

Fires and other climate-related issues such as reduced rainfall are likely to interfere with the restoration effort in the coming years. The scientists view their effort as a multi-generational one: a new cohort of stewards will need to take their place in the ensuing decades. 

"To be successful, the translocated populations must become self-sustaining, and the benchmark is the appearance of second-generation seedlings," the researchers said. "Given the slow growth and maturation of Wollemi pines in the wild, this is likely to take many decades, if not centuries. Given predicted increases in the frequency and severity of fire and drought due to climate change — arguably the two greatest threats to these populations — their long-term security is far from guaranteed."

66 million years ago, the last dinosaurs vanished from Earth. We're still trying to understand why. New fossils of abelisaurs —  distant relatives of the tyrannosaurs —  from north Africa suggest that African dinosaurs remained diverse up to the very end. And that suggests their demise came suddenly, with the impact of a giant asteroid.

The causes of the mass extinction have been debated for two centuries. Georges Cuvier, the father of palaeontology, thought extinction was driven by catastrophes. Charles Darwin  thought gradual changes in the environment and competition between species slowly drove lineages extinct.

As our understanding of the fossil record improved, it became clear that the Cretaceous period (145 million years to 66 million years ago) ended with an extraordinary wave of extinction. Huge numbers of species disappeared, worldwide, in a brief period. The discovery of the 180km-wide Chixculub asteroid impact crater in Mexico suggested a sudden extinction of dinosaurs and other species, driven by the impact. But others have argued that a long, slow decline in dinosaur diversity contributed to their extinction.

Piecing together the story is hard. It's not just that dinosaur fossils are so rare; the fossil record is also patchy.

Most of what we know about the dinosaurs' final days is the result of intensive study of a few places in the United States, Canada and Mongolia. Far less is known about dinosaurs of the southern landmasses — South America, India, Madagascar, Australia, Antarctica, New Zealand.

Partly that's down to geography; it's hard to find dinosaurs in rainforests. Partly there have, historically, just been more palaeontologists and museums in the northern hemisphere. The question is whether the picture is biased.

Because it's such a huge landmass, Africa probably had far more dinosaur species than North America. Yet until recently we've known hardly anything about Africa's end-Cretaceous dinosaurs. Africa has few terrestrial rocks from this period. That's because high levels of volcanic activity pushed sea levels up, submerging much of Africa under shallow seas. Dinosaurs, being terrestrial, rarely occur in marine rocks. But rarely doesn't mean never. Study enough marine fossils, you eventually find a dinosaur.

And in Morocco, we've studied lots of marine fossils.

What we've found

The phosphate deposits of Morocco are the remains of an ancient seabed, dating to the final million years of the dinosaur era. They're full of fish bones and scales, shark teeth and marine reptiles. Vast numbers of marine reptiles —  mosasaurs, plesiosaurs, sea turtles.

But once in a while, dinosaurs turn up.

It's not clear how dinosaur bones ended up in marine sediments. Dinosaurs may have swum out to islands searching for food, as deer and elephants do today, and some might have drowned. Other dinosaurs might have been washed out to sea by floods or storms, or drowned in rivers that carried them downstream to the ocean. Still others may have died on the shoreline before being carried out on a high tide. But some improbable series of events transported dinosaurs into the ocean.

And so, studying marine beds, and working over many years, we've slowly put together a picture of Africa's last dinosaurs, bone by bone.

Africa's last dinosaurs included titanosaurian sauropods, long-necked plant-eaters the size of elephants. Horse-sized duckbill dinosaurs filled the herbivore niche. But the carnivores are particularly interesting. Sitting at the top of the food chain, they tell us a lot about the ecosystem. And African predatory dinosaurs were diverse, implying diverse herbivores, and lots of them.

The top predator was a ten-metre-long animal called Chenanisaurus barbaricus. So far Chenanisaurus is known from just a jawbone, but this tells us it was part of the Abelisauridae, a bizarre family of carnivores found in South America, India, Madagascar and Europe, while tyrannosaurs dominated in the north. Abelisaurs had short, bulldog snouts, and sometimes horns, and they had bizarre, stumpy little arms that make the arms of T. rex look massive by comparison.

Now, fossils of two new abelisaurs have appeared in Morocco.

One is known from a tibia, a shin bone. It was smaller than Chenanisaurus, about five metres long —  small by dinosaur standards, but large compared to modern predators. Curiously, it resembles abelisaurs found in South America. It's possible this marks an ancient land connection that existed between the continents 100 million years ago. Or, abelisaurs may have swum the narrow seaway separating the continents.

Another bone is from the foot of an even smaller abelisaurid, just three meters long. Similar small abelisaurids occur in Europe; it may be related to them.

In recent months, more dinosaur fossils and more species have turned up. We're still writing these fossils up, so we can't say much now, but finding so many species in a handful of fossils tells us we're sampling from a highly diverse fauna.

While fossils from the Great Plains in North America may record a decline in dinosaur diversity, this may be a local phenomenon, not a global one. It's possible global cooling in the latest Cretaceous hit higher-latitude environments hard, reducing diversity. But the African dinosaur fauna hints that at low latitudes, dinosaurs were thriving, even diversifying. If so, that means dinosaurs were cut down in their prime; burning out rather than fading away.

What our findings show

Africa's last dinosaurs, especially its diverse predatory dinosaurs, suggest that immediately before their extinction, the dinosaurs thrived.

For over 100 million years, they evolved and diversified, producing a remarkable range of species: predators, herbivores, aquatic species, even flying forms, the birds. Then in a single, catastrophic moment, everything was wiped out in the months of darkness caused by dust and soot from the impact. Everything, except a half-dozen or so bird species.

Evolution is driven by rare, improbable events like asteroid impacts. Curiously, science is often driven forward by improbable events as well —  like the unlikely discovery of dinosaurs buried millions of years ago, at the bottom of the sea.

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

A fossilized frog that lived alongside the dinosaurs 100 million years ago has been discovered with a belly full of eggs — the oldest such frog ever found, scientists have announced.

Researchers believe the frog was likely killed during mating, when the female may have been drowned by a male that was gripping her.

Frogs do not get pregnant. Instead, female frogs develop a batch of eggs that they are ready to lay, in what is known as a "gravid" state. The eggs are eventually laid and fertilized by a male.

The gravid frog, from the species Gansubatrachus qilianensis, was found in a fossil bed in northwest China and dates from the Cretaceous period (145 million to 66 million years ago), researchers revealed in a study published Feb. 6 in the journal Royal Society B: Biological Sciences.

Fossilized frogs from this period are  exceedingly scarce, and those that have preserved soft tissues are even rarer. This specimen is more extraordinary still, as it's the earliest documented record of a gravid frog, the researchers noted.

Related: These female frogs fake their own deaths to get out of sex

The scientists compared the fossilized gravid frog with other previously discovered specimens. They built  a high-resolution model of its skeleton using computed tomography (CT) scans of the fossils, and analyzed the composition of its eggs using X-rays.

Their analysis suggested that the frog was still skeletally immature, meaning she was able to sexually reproduce before being physically fully developed. Though this is common in many modern animals, there was previously no direct fossil evidence that this was the case for ancient frogs and toads.

"The evolution of reproduction, especially reproductive strategies, is a very important part of biological evolution," lead author Baoxia Du, a paleontologist at Lanzhou University in China, told Live Science.

Understanding the reproductive strategies employed by early frogs could offer valuable insights into their complete reproductive history, he added.

As the frog was skeletally immature, the researchers ruled out old age as her cause of death. Environmental factors, such as abrupt changes in water conditions or algae blooms, were also unlikely, as evidence of this would've been apparent in the deposits studied, Du said.

Few other frog fossils were found in the deposits, suggesting that some disastrous event was not the culprit as it would have led to a mass death and numerous frog fossils nearby.

"We currently believe that the most likely cause of death is weakness or even suffocation after 'amplexus behavior,' which is quite common among existing frogs,” Du said.

Amplexus, which means embrace in Latin, describes the behavior when males mount and grip onto females with their front legs for hours or days at a time until her eggs are fertilized. In doing this, the female may have died from drowning or exhaustion, according to the study.

While more fossil records are required to substantiate the findings that early frogs were sexually mature before adulthood, the discovery provides a tantalizing glimpse into the development of ancient frogs. "The fact that [early frogs] thrived during the dinosaur era and endured multiple mass extinctions makes studying their survival strategies highly valuable," Du said.

Paleontologists have uncovered a never-before-seen tyrannosaur species in North America that has been masquerading as a Tyrannosaurus rex for decades. The newly identified species is the closest known relative of T. rex and could have been even larger than the dinosaur king, a new study shows.  

The newfound sister species, Tyrannosaurus mcraeensis, was identified from a partial fossilized skull that paleontologists unearthed in 1983 while exploring the Hall Lake Formation in New Mexico. The calcified cranium was originally classified as a T. rex skull and has been displayed at the New Mexico Museum of Natural History and Science (NMMNHS) ever since. But in 2013, a team of paleontologists decided to reevaluate the skull after noticing subtle yet suspicious anomalies in its shape.  

In a new study published Thursday (Jan. 11) in the journal Scientific Reports, the team revealed that the skull dates to between 73 million and 71 million years ago during the Cretaceous period (145 million to 66 million years ago). This makes T. mcraeensis between 3 million and 5 million years older than T. rex.

The stark age difference was the main giveaway that they had discovered a new species. But there were also major morphological differences that stand T. mcraeensis apart from the infamous dinosaur king.

"The most striking difference is the shape of the lower jaw, which is more slender and curved [than T.rex]," study co-author Nick Longrich, a paleontologist at the University of Bath in the U.K., told Live Science. "It also lacks the prominent bosses or hornlets found over the top of the eyes in T. rex."

T. mcraeensis also has fewer teeth than most other tyrannosaurs, which is one of the main reasons why the researchers believe it is T. rex's closest relative — because T. rex also has fewer teeth, Longrich said. 

Related: Nanotyrannus vs. T. rex saga continues: Controversial study 'doesn't settle the question at all'

The size of the skull suggests this particular T. mcraeensis was around the same size as a typical adult T. rex, which grew to around 39 feet (12 meters) long — around the same size as a double-decker bus. But other individuals of the same species may have been even larger.

"It's not impossible" that T. mcraeensis could have been even larger than T. rex, Longrich said. "Since we only have one individual, it's unlikely we've found the biggest individuals of the species."

T. mcraeensis was likely the apex predator of its time, just like T. rex, Longrich said. And if the pair had existed at the same time, they would have "probably been pretty evenly matched" in a fight, he added.

T. rex and most other tyrannosaurs lived exclusively on an ancient landmass known as Laramidia, which was made up of what is now the western coast of North America from Alaska down to Mexico.

Until now, T. rex's closest relatives were a pair of tyrannosaurs named Tarbosaurus bataar and Zhuchengtyrannus magnus, which are found in modern-day China and Mongolia. Both species dated back further than T. rex, which suggests tyrannosaurs may have first emerged in what is now Asia, although this has never been confirmed. 

The new findings suggest that Laramidia is a more likely origin of the tyrannosaur lineage, which would imply that these dinosaurs later spread to Asia. However, there is still uncertainty around this.

Laramidia was home to a wide variety of dinosaur species, including several other recent discoveries, such as Sierraceratops turneri — a horned herbivore similar to Triceratops that was described in a 2022 paper and was also previously misidentified as a different dinosaur species.

The new findings are further evidence that New Mexico is one of the best places in the world to search for new dinosaur species, study co-author Spencer Lucas, the curator of geology and paleontology at NMMNHS, said in a statement sent to Live Science. "Many new dinosaurs remain to be discovered in the state, both in the rocks and in museum drawers," he added.

Researchers have discovered the earliest bird footprints ever found in Australia, showing that these early birds once lived in southern polar regions on the supercontinent Gondwana.

Palaeontologists unearthed the bird tracks in Wonthaggi Formation in Victoria, Australia, that date back to around 120 million years ago, during the Early Cretaceous (145 million to 100.5 million years ago). 

Prior to these findings, there has been minimal evidence of Early Cretaceous birds in Australia — consisting of limited skeletal material, feathers and two tracks. At that time, what is now Australia was part of Gondwana and was further south, sitting near the South Pole.

"These bird tracks are scientifically important for several reasons. For one, they’re the oldest in Australia, telling us that birds have been living in Australia for at least 120 million years. But they’re also the oldest bird tracks in the Southern Hemisphere, which covers a lot more of the Cretaceous world," study co-author author Anthony Martin, a paleontologist at Emory University in Atlanta, Georgia, told Live Science. 

"These tracks are from when this part of Australia was still connected to Antarctica and close to the South Pole then. So this makes them the oldest bird footprints from formerly polar environments."

Related: Extinct 'Lord of The Rings' eagles had a 10-foot wingspan and probably could have carried a hobbit

Researchers say the tracks give insight into how early birds dispersed across landmasses and biomes. Cretaceous bird fossils are extremely rare in southern regions — unlike in the northern continents, where a diverse range of early bird fossils have been found. The study, published Nov. 15 in the journal PLOS ONE, describes 27 bird footprints of varying sizes and shapes, which are evidence that several ancient bird species lived in the region, including some of the largest known birds from the Cretaceous. 

The researchers identified the tracks as belonging to avian animals  because they were tridactyl (meaning they had three digits on a foot), with thin digits and sharp claws. 

The bird tracks were discovered on marine outcrops that would once have been an ancient polar floodplain, suggesting that the area could have been part of a migratory route during polar summers, the researchers suggest in the study. 

The authors suggest the fossilized tracks are evidence of seasonal behaviors, as the birds would have walked across the surface of the beds after the weather thawed in the spring season. It also suggests that Early Cretaceous birds might have flown to what is now Australia from northern regions of Gondwana during Southern Hemisphere springs. 

"Because these bird tracks were made in polar environments at least 120 million years ago, and they were preserved on what were then river floodplains, we think this shows that birds were living in these places during the summers there, after spring thaws," Martin said. "That further implies that they probably aren't living there during cold, dark winters, so they may have migrated seasonally to and from other environments."

The researchers hope the new finds will inspire others to look for more evidence of Cretaceous birds in the Southern Hemisphere. "We can then better understand where birds dispersed early in their evolutionary history, and about when they started changing the world," Martin said.

Just beneath the scrubby plains of southern North Dakota at the site of an ancient riverbed, paleontologists are hard at work digging up the end of the world as the dinosaurs knew it. 

Now, they've discovered two newfound species of 66 million-year-old sturgeon that lived and died alongside dinosaurs, preserved as fossils in exquisite three-dimensional detail. Their work was published in the Journal of Paleontology on Oct. 3. 

The team found the fossils at a site called "Tanis," named after the purported last resting place of the Ark of the Covenant in the 1981 movie "Raiders of the Lost Ark." Tanis is a section of the famous Hell Creek Formation, which spans parts of Montana, South Dakota, North Dakota and Wyoming, and it was once home to a large, deep river that fed the now-dry Western Interior Seaway that stretched from the Gulf of Mexico to the Arctic Ocean. But one fateful day 66 million years ago, Tanis became a mass grave for thousands of ancient freshwater fish, which were smothered and buried in place in the blink of an eye, possibly in the minutes after the asteroid impact that wiped out the nonavian dinosaurs. 

"It was really amazing," Lance Grande, a paleontologist at the Field Museum in Chicago and co-author of the study, told Live Science. "I mean, [the fish] were stacked up like cordwood."

Related: Photos: Cretaceous 'Graveyard' Holds a Snapshot of the Dino-Killing Asteroid Impact

After years of excavation, Grande and his colleagues finally got the chance to begin studying the fossil fish up close. They quickly realized that four (two of each species) of the specimens were something special. Almost all of the creatures' bony outer coverings, or scutes, were intact and impeccably preserved. And the specimens help fill a gap in North America's fossil record, which lacks many late Cretaceous species. "They have a lot of clear sturgeon similarities, which makes them easy to identify," Grande said. "But they have various unique features that allow us to describe them as something new."

The researchers dubbed one of the newfound species Acipenser praeparatorum ("acipenser" means "sturgeon" in Latin, and "praeparatorum" translates as "to make ready," in honor of the team that prepared the fossil prior to its investigation); they named the other species Acipenser amnisinferos, or the "sturgeon from Hell's Creek.") Both fish species are extinct today. However, they bear an unexpected resemblance to modern-day sturgeon that are native to East Asia and Europe, rather than North America, study co-author Eric Hilton, an evolutionary biologist at the Virginia Institute of Marine Science, told Live Science.

Sturgeons and their relatives are particularly distinctive in the fossil record. "They have these big, bony plates on the outside," Hilton explained, which protect the fishes' corpses from being torn apart by waves or strong river currents that tend to pulverize the remains of more delicate fishes. And since exposure to lots of oxygen tends to break down body tissues before they can fossilize, sturgeons' preference for low-oxygen environments sets them up for preservation. 

For the sturgeons at the Tanis site, however, it wouldn't have mattered how much oxygen was in the water on the day they died; they were the victims of a massive tidal wave that swept thousands of pounds of sediment into the river, burying them almost instantly. Scientists suspect that this wave was triggered by the same dinosaur-killing Chicxulub asteroid that smacked into the Yucatán Peninsula — Tanis is littered with tiny, telltale beads of glass, called tektites, that are chemically identical to those found at the Chicxulub crater, Live Science previously reported. Like the rest of the Hell Creek Formation, Tanis today is a snapshot of the end of the Mesozoic era. 

In addition to the two newly described sturgeon species, the river was chock-full of paddlefish, bowfish, ammonites, various insects and aquatic reptiles called mosasaurs. And, the researchers suspect, there are probably many more species lurking in the sediments, waiting to be excavated. 

"This is awesome," said Hilton, "But it's the tip of the iceberg." 

The Cretaceous period was the last and longest segment of the Mesozoic era. It lasted approximately 79 million years, from the minor extinction event that closed the Jurassic period about 145 million years ago to the Cretaceous-Paleogene (K-Pg) extinction event 66 million years ago. The name comes from "creta," the Latin word for chalk, because of widespread chalk deposits dating from the period, according to the National Park Service.

In the early Cretaceous, the continents were in very different positions than they are today, according to the Australian Museum. Sections of the supercontinent Pangaea were drifting apart. The Tethys Ocean still separated the northern continent Laurasia from the southern continent Gondwana. The North and South Atlantic were still closed, although the Central Atlantic had begun to open up in the Late Jurassic period. By the middle of the Cretaceous period, ocean levels were much higher; most of the landmasses we are familiar with were underwater. By the end of the period, the continents were much closer to their modern configuration. Africa and South America had assumed their distinctive shapes. But India had not yet collided with Asia, and Australia was still part of Antarctica.

Cretaceous period plants

One hallmark of the Cretaceous period was the development and radiation of flowering plants, or angiosperms, which "rapidly diversified," according to the National Park Service. This radiation "gave rise suddenly and mysteriously to exquisite angiosperm diversity in the mid-Cretaceous," an evolutionary development that troubled Charles Darwin, who saw evolution happening much more slowly, according to a review in the journal Proceedings of the Royal Society B. Darwin proposed that flowering plants must have started developing long before the Cretaceous, potentially on "a lost island or continent," William E. Friedman, an evolutionary biologist at Harvard University, wrote in the American Journal of Botany in 2009. However, the Cretaceous-era burst of floral development may instead reveal how evolution can happen very quickly, Friedman wrote.

Though Darwin's lost continent never showed up, some flowering plants may have appeared in the Jurassic, recent research has shown.  

However, Jurassic-era flowering plants would have been uncommon and may also have been evolutionary links between older plants that resembled angiosperms and the real thing, found in the Cretaceous, researchers said. Scientists generally place "the oldest uncontested" angiosperm fossils at about 125 million to 130 million years ago, in the early Cretaceous, according to the Brooklyn Botanic Garden. These include plants of the genera Archaefructus and Montsechia, which show the first evidence of ovaries in plants but may have lacked petals. 

Since Darwin, scientists have thought that pollinating insects, such as bees and wasps, played a key role in the Cretaceous explosion of flowering plants, according to recent and foundational research. This is frequently cited as an example of co-evolution, according to the Washington Native Plant Society. 

The mid-Cretaceous saw abundant populations of both insects and flowering plants, and recent finds finally caught Cretaceous-era insect pollinators frozen in the act. In 2019, scientists reported in the journal Proceedings of the National Academy of Sciences the first direct fossil evidence of insect pollination in the Cretaceous: a tumbling flower beetle, Angimordella burmitina, preserved in amber since the mid-Cretaceous, 99 million years ago, and covered with pollen grains. The beetle sports several body parts specialized for feeding on flowers, including pollen-feeding mouthparts, and the pollen grains have traits, like clumping characteristics, associated with insect pollination, the researchers reported.

And in a 2020 paper published in the journal BioOne, scientists reported on the oldest bee found bearing pollen, the 100 million-year-old Discoscapa apicula. Also found encased in amber, this insect shared some traits with modern bees, such as hind legs laden with pollen, and some traits with wasps, such as its wing vein features.

Thanks to pollinating insects, flowering plants had tremendous advantages over plants that spread pollen only by wind, spurring the explosion of angiosperms, according to Illinois Extension at the University of Illinois Urbana-Champaign. Competition for insect attention probably facilitated the relatively rapid success and diversification of the flowering plants, "lead[ing] to the development of many different size, shapes, colors and fragrances of flowers we see today,” including the production of nectar to attract hungry bugs. As diverse flower forms lured insects to pollinate them, insects adapted to different ways of gathering nectar and moving pollen, thus setting up the intricate co-evolutionary systems found to this day.

A few finds over the decades have estimated that some pollinating insects arrived before flowering plants. In 2009, researchers found that 11 species of scorpionflies present starting in the middle Jurassic boasted the elongated mouthparts and pollen-centric diets characteristic of pollinators, as reported in the journal Science. These likely pollinating insects, however, fed on nonflowering plants, or angiosperms, "long before the similar and independent coevolution of nectar-feeding flies, moths and beetles on angiosperms," the study said. These critters went extinct during the Cretaceous, around the time of the "global gymnosperm-to-angiosperm turnover," the researchers said. In the 1990s, researchers reported that bee- or wasp-like insects built hive-like nests in what is now called the Petrified Forest in Arizona, dating back to more than 200 million years ago. However, later re-evaluations found that the structures lacked defining characteristics of bee nests and most likely came from beetle larva chambers or other creatures, as reported in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. That evaluation of the structures "eliminates them as evidence that decouples bee origins from the Cretaceous origin of angiosperms," the scientists wrote.

Some evidence shows that dinosaurs ate flowering plants. Two dinosaur coprolites (fossilized excrements) discovered in Utah contain fragments of angiosperm wood, according to an unpublished study presented at the 2015 Society of Vertebrate Paleontology annual meeting. An Early Cretaceous ankylosaur was found with fossilized angiosperm fruit in its gut. 

However, for the most part, evidence suggests that dinosaurs ignored angiosperms in the Cretaceous, maintaining a diet focused on ferns and conifers, University of Bristol researchers said in 2021, summarizing their work on angiosperm evolution in the journal New Phytologist. The shape of some teeth from Cretaceous animals suggests that the herbivores grazed on leaves and twigs, said Betsy Kruk, formerly a volunteer researcher at the Field Museum in Chicago and now a principal investigator and project manager at Material Culture Consulting, a California-based company that consults on compliance services including archaeology and paleontology.

Cretaceous period animals

The Cretaceous was an age of reptiles. Dinosaurs dominated the land, while marine reptiles like the mosasaurs — which could span 56 feet (17 meters) — swam the oceans. Pterosaurs plied the skies, including the largest flying animal ever, Quetzalcoatlus, whose wingspan could stretch to 36 feet (11 m). 

The largest-ever land predator, the famous Tyrannosaurus rex, also reigned during the Cretaceous. By the end of the Jurassic, some large sauropods, such as Apatosaurus and Diplodocus, had gone extinct. But other giant sauropods, including the titanosaurs, flourished, especially toward the end of the Cretaceous, Kruk said. Titanosaurs were the most successful sauropods of the period, and the past two decades have seen a "boom" in titanosaur discoveries, according to the journal Nature Ecology & Evolution. 

Large herds of herbivorous ornithischians also thrived during the Cretaceous. These included Iguanodon (which belongs to the same group as duck-billed dinosaurs, also known as hadrosaurs), Ankylosaurus, and the ceratopsians, like Triceratops. Duck-billed dinosaurs were the most common type of ornithischians, a group of mostly herbivorous dinosaurs with bird-like hips, according to the Cal Poly Humboldt Natural History Museum. Theropods, including T. rex, continued as apex predators until the end of this period.

During the Cretaceous, more ancient birds took flight, joining the pterosaurs in the air. Experts have long debated the origin of flight. According to the so-called trees down theory, small reptiles may have evolved flight from gliding behaviors. The ground up hypothesis posits that flight evolved from the ability of small theropods to leap high to grasp prey or evade predators. Early research suggested that feathers evolved from elongated scales whose primary function, at least at first, was thermoregulation. They could be moved to absorb more solar heat in cool conditions and provide protection from the sun when it was hot, according to a 1975 study in The Quarterly Review of Biology. More recent studies suggest that signaling and tactile sensing may also have played a role in the evolution of these feather precursors, according to a study in the International Journal of Organic Evolution. 

The earliest fossilized bird, Archaeopteryx, swooped through Cretaceous skies 150 million years ago, though it resembled small dinosaurs more than the birds we see today, according to the Australian Museum. A variety of birds arrived on the scene soon afterward sporting a range of features that could be more like those of current birds. Some of these creatures evolved into birds of the modern type by the late Cretaceous, which means that "bird-like dinosaurs, primitive birds and early modern birds all co-existed" for a stretch of the Cretaceous, the Australian Museum added.

One Cretaceous-era bird, Confuciusornis sanctus, lived about 125 million years ago. It was a crow-size bird with a modern, toothless beak, unlike the fanged Archaeopteryx; claws similar to those of modern, tree-dwelling birds; and flight-worthy feathers. A study of pigment-storing cell organelles in C. sanctus in the journal Science found that these ancient birds likely sported dark feathers on their torsos, with lighter-colored wings, according to the California Academy of Sciences. Iberomesornis, a contemporary of Archaeopteryx only the size of a sparrow, was capable of flight and may have been an insectivore. 

Related: Are birds dinosaurs?

Sea creatures also thrived during the Cretaceous, with many marine groups reaching their peak levels of diversity, according to the Cal Poly Humboldt museum. Beyond the mosasaurs, ocean sea life included mollusks that built reefs comparable to today's coral reefs, along with sharks, lobsters and crabs, sand dollar-like creatures known as echinoids, and a type of bony fish known as ray-finned fish (named for their fins formed from spines draped with webs of skin).

Though reptiles ruled the Cretaceous world, early mammals did exist at the time. Traditionally, scientists have viewed mammal evolution as constrained by the dominant dinosaurs; mammals couldn't evolve many species types, because dinosaurs occupied most niches, this view suggests. Only after the mass extinction that killed off all nonavian dinosaurs could mammals "radiate," or evolve into many diverse forms. But mammals may have gone through radiations even during the dinosaur age, including the Jurassic and Cretaceous periods, a 2019 study in the journal Trends in Ecology and Evolution found. And a 2021 study in the journal Current Biology found that evolutionary suppression of therians, the ancestors of today's mammals, may have come from not only dinosaurs, but also ancient relatives of mammals known as mammaliaforms.

How did the Cretaceous period end?

About 66 million years ago, nearly all large vertebrates and many tropical invertebrates became extinct in one of Earth's five great mass extinction events, according to former University of California, Davis, Earth and planetary sciences professor Richard Cowen. Scientists have linked that mass extinction with an enormous asteroid that collided with Earth in what is now Mexico. The event killed off all nonavian dinosaurs, all pterosaurs (which were not dinosaurs) and many marine reptiles, including mosasaurs and plesiosaurs, as well as many early mammals and "a host of amphibians, birds, reptiles and insects," according to the American Museum of Natural History in New York. An estimated three-quarters of species alive at the time met their end. 

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

Geologists call this mass die-off the K-Pg extinction event because it marks the boundary between the Cretaceous and Paleogene periods; the "K" is from "Kreide," the German word for Cretaceous. The event was formerly known as the Cretaceous-Tertiary (K-T) event, but the group that sets standards for geologic nomenclature now considers Tertiary out of date with current science, according to the National Commission for Stratigraphy Belgium. 

The Chicxulub (CHEEK-sheh-loob) crater in the Yucatán Peninsula, which spans more than 110 miles (180 kilometers) in diameter, is the likely landing spot of the dinosaur-killing asteroid. This crater dates to within 33,000 years of the K-Pg event, Live Science previously reported. "We've shown the impact and the mass extinction coincided as much as one can possibly demonstrate with existing dating techniques," Paul Renne, lead scientist in that study and a geochronologist and director of the Berkeley Geochronology Center in California, previously told Live Science.

Scientists had first associated the K-Pg extinction with an extraterrestrial impact decades ago, however. In 1979, a geologist discovered that the thin layer of clay separating the Cretaceous and Paleogene periods contained high concentrations of iridium. This element is rare on Earth but much more common in meteorites and asteroids, according to the Lunar and Planetary Science Institute. Other researchers found "shocked quartz," a form of the mineral created under intense pressure, and tiny, glass-like globes called tektites that form from droplets of melted rock. Both of these geological features form when an extraterrestrial object strikes Earth with great force.

Research in 2020 found that the object that carved out Chicxulub hit Earth at the most destructive possible angle, Live Science previously reported. The 7.5-mile-wide (12 km) asteroid, traveling at about 27,000 mph (43,000 km/h), would have vaporized rocks, sending 325 gigatons of sulfur and 435 gigatons of carbon dioxide into the atmosphere in the form of pulverized rock and sulfuric acid droplets, researchers estimated.

When the asteroid collided with Earth, its impact would have triggered a 10.1-magnitude earthquake, sent a shock wave with "hurricane-force winds" rippling across the Americas, and spawned a 330- to 820-foot-high (100 to 250 m) tsunami, according to a 2021 University of Maryland course. As debris ejected by the impact fell back to Earth, the material would have cooked the atmosphere to 2,700 degrees Fahrenheit (1,482 degrees Celsius), painting the sky red for several hours and igniting forest fires across the planet, Live Science reported in 2013. The heat pulse was like a global broiler oven, not only burning vegetation, but also cooking living things unable to burrow or dive, the researchers said.

"This rain of hot dust raised global temperatures for hours after the impact and cooked alive animals that were too large to seek shelter," Kruk said. "Small animals that could shelter underground, underwater, or perhaps in caves or large tree trunks, may have been able to survive this initial heat blast."

Rock vaporized by the asteroid likely stayed in the atmosphere, blocking part of the sun's rays for months or years, according to the University of Maryland. This may even have lasted as long as 16 years, with a 30-year recovery period. With less sunlight, plants would have died, with consequences traveling up the food chain to herbivores dependent on plants and carnivores dependent on those herbivores, according to the Natural History Museum in London. 

Furthermore, the reduced sunlight would have drastically lowered global temperatures, which plunged in the tropics from 81 F (27 C) to 41 F (5 C), Live Science previously reported. The newly frigid climate would have impaired large active animals with high-energy needs, Kruk said.

"Smaller, omnivorous terrestrial animals — like mammals, lizards, turtles or birds — may have been able to survive as scavengers feeding on the carcasses of dead dinosaurs, fungi, roots and decaying plant matter, while smaller animals with lower metabolisms were best able to wait the disaster out," she said. 

The last phase of the asteroid fallout, greenhouse warming, may have lasted around 100,000 years, according to the University of Maryland. Carbonite rocks oxidized by the impact would have released large amounts of the greenhouse gas carbon dioxide (CO2) into the atmosphere. Just before the impact, a series of what may have been the second-largest volcanic eruptions ever on land went off at the Deccan traps in western India, according to the American Museum of Natural History. These regional catastrophes had already spewed tremendous levels of CO2 and so likely combined with the asteroid fallout to heat up the planet once the sun-obscuring dust settled, according to the University of Maryland.

Cretaceous period climate

Even before global cataclysms spurred global warming, the world was a warmer place during the Cretaceous period than it is today, according to Climate Policy Watcher. The poles were cooler than the lower latitudes, but "overall, things were warmer," Kruk told Live Science. Fossils of tropical plants and ferns support this idea, she said. Warm ocean currents, unfrozen poles and levels of CO2 that were relatively high even before the extinction event all combined to produce a hot planet, according to Climate Policy Watcher. 

Animals in the Cretaceous lived all over, even in colder areas. For instance, Hadrosaur fossils dating to the Late Cretaceous were uncovered in Alaska. And in a 2020 paper in the journal Nature, scientists reported on a temperate rainforest in Antarctica dating to the mid-Cretaceous.

Additional resources

Learn about and visit a cast of a titanosaur, the gigantic sauropods of the Cretaceous era, at the American Museum of Natural History. Explore the Cretaceous-Paleogene extinction and Earth's four other mass extinction events, including the possibility that we've entered a new one, at the Natural History Museum in London. Discover how pollinators and flowers have co-evolved at the New England Primate Conservancy. Read Richard Cowen's essay on the K-Pg mass extinction event and other topics in his book "History of Life" (Blackwell Scientific Publications, 2000).

This article was originally written by Live Science contributor Mary Bagley with contributions from Live Science editor Laura Geggel.

Originally published on Live Science on January 8, 2016 and updated on July 26, 2022.

Researchers in Argentina have unearthed the largest pterosaur species ever found in South America. Dubbed "dragon of death" by paleontologists, two giant flying reptiles were discovered in the Plottier Formation, an outcrop located in the province of Mendoza.

The two specimens' wingspans measured approximately 23 feet (7 meters) wide and 30 feet (9 m) wide, respectively. Researchers confirmed that they are azhdarchids, a family of pterosaurs that lived during the end of the Cretaceous period (approximately 146 million to 66 million years ago). 

"Azhdarchids were known for their very large skulls — sometimes larger than their bodies — as well as their hyper-elongated necks and short, robust bodies," Leonardo D. Ortiz David, lead author of a new study describing the enormous pterosaurs and coordinator general of Argentina's Laboratory and Museum of Dinosaurs in Mendoza, told Live Science in an email.

The scientists identified the pterosaurs as two individuals in the species Thanatosdrakon amaru. This is the sole species in the genus, which means "dragon of death," in Greek. The species name, "amaru," translates as "flying serpent" from the Indigenous Quechuan language and refers to Amaru, a two-headed Incan deity, the study authors reported. 

Related: 'Real-life dragon' in Cretaceous Australia was huge, toothy and a 'savage' hunter

Researchers determined that the two pterosaurs died at the same time and that one was not yet fully grown. But the scientists can't say for sure if the two animals represent part of a family group.

"There is no indication in the fossil remains of a degree of parental relationship," Ortiz David said. "However, it can be confirmed that both specimens are of different sizes, and that the smaller one is a juvenile-subadult, and that they were together when they died more than 86 million years ago."

The fossils were found during excavations for a civil construction project about 500 miles (800 kilometers) outside Mendoza's capital city (also named Mendoza). Ortiz David and his team were supervising the dig when they discovered fossil fragments within floodplain deposits. Mendoza, where Aconcagua, the highest mountain in the Americas, is also located, is well known among paleontologists for other important dinosaur discoveries, including that of the giant sauropod Notocolossus, one of the largest dinosaurs in the world, in 2016. (Ortiz David's research group made that discovery as well.) 

"The [Thanatosdrakon] fossils were in different states of preservation; some of them were complete, such as both humeri [large arm bones], syncarpals [fused foot bones] and dorsal vertebrae," he said. "Others were fragmentary, including the phalanges [toe bones], ulna, radius [forearm bones], femur [upper leg bone] and pelvis."

Ortiz David said that the team's discovery of fossils in such good condition was surprising, because pterosaur bones are fragile, and fossils are usually found in tiny pieces.

"From the beginning, two facts caught our attention: The first was the size of the remains and their preservation in three dimensions, an unusual condition in this group of vertebrates; the second was the amount of remains found at the site, since large-giant pterosaurs are only known from fragmentary remains (with some exceptions)," he said. "The description of new specimens is always important for vertebrate paleontology, as they shed light on the different groups being studied. In this particular case, 3D elements of large pterosaurs are scarce, making Thanatosdrakon an excellent case study."

The fossils are currently housed in the Laboratory and Museum of Dinosaurs  at the National University of Cuyo in Mendoza. To help preserve the specimens, museum experts made casts of the different fossils on a 1-to-1 scale; the casts are on display at the museum. 

The researchers' findings will be published in the September 2022 issue of the journal Cretaceous Research.

Originally published on Live Science.

Tyrannosaurus rex youngsters paddle through shallow ocean water near a sandy shore, their powerful legs working hard to make up for their disproportionately tiny arms. Long-necked sauropods nuzzle their heads together in affectionate mating displays. And packs of duck-billed dinosaurs raise dust clouds as they migrate across vast deserts. These and other scenes in the official trailer for "Prehistoric Planet," a new documentary series from Apple TV+, offer a glimpse of dinosaurs and their Cretaceous neighbors, much in the way a nature documentary would feature dramatic moments in the lives of modern animals. 

Released on April 20, the trailer showcases stunning footage from around the world, combined with astonishingly realistic computer-generated imagery, to bring an assortment of Cretaceous creatures back to life — and to challenge what viewers thought they knew about these animals that once dominated ecosystems on every continent.

The new five-part series introduces habits, lifestyles and behaviors of long-extinct species and shows how dinosaurs that lived millions of years ago interacted, Apple TV+ representatives said in a statement.

With scenes that unfold beneath the ocean's surface to brutal battles on icy plateaus, the trailer features diverse habitats and offers a fresh perspective on a variety of dinosaurs, from the famed Triceratops to the less-familiar, heavily armored and tanklike Nodosaurus. 

Related: 10 extraordinary dinosaur discoveries from 2021

Renowned nature documentary presenter Sir David Attenborough narrates the series, and the trailer hints at untold stories about thrilling mating competitions between colossal sauropods; standoffs between theropod predators and Triceratops prey; and the nesting habits of cliff-dwelling pterosaurs. (Pterosaurs were flying archosaurs, not dinosaurs, but they lived alongside dinosaurs during the Jurassic, Triassic and Cretaceous periods.) 

Recent discoveries in paleontology informed how the dinosaurs and other Cretaceous animals of "Prehistoric Planet" look, move and behave, according to Apple TV+. Viewers will meet two relatively recently discovered species of tyrannosaur: Qianzhousaurus rex from eastern China, described in 2014 in the journal Nature Communications, and the diminutive Nanuqsaurus — whose name means "polar bear lizard," taken from the Alaskan Inupiat word "Nanuq" — which was also described in 2014, in the journal PLOS One.

Qianzhousaurus was slightly smaller and more slender than T. rex, Live Science reported in 2014. It had a long snout, which led scientists to lend it the nickname "Pinocchio rex."

Other well-known dinosaurs, such as Velociraptor, have previously appeared in popular movies wearing scaly, lizard-like skin, but in the "Prehistoric Planet" trailer, these dinosaurs are covered in feathers, reflecting recent discoveries about how commonly feathers appeared across the theropod lineage. In one of the trailer's most dramatic images, an extreme close-up of a Velociraptor's enormous claw hints at further adaptations that contributed to this dinosaur's reputation as a deadly predator.

We'll be bringing you more sneak peeks of this series in the coming weeks, check back here at Live Science for more theropod teasers and sauropod surprises!

"Prehistoric Planet" premieres May 23 on Apple TV+.

Originally published on Live Science.

Spring is a time for budding flowers, tender green leaves and baby animals. But 66 million years ago, that gentle season instead brought mass death and carnage from Earth's catastrophic impact with a massive space rock.

Earth was forever changed after an enormous asteroid smashed into our planet at the end of the Cretaceous period (145 million to 66 million years ago), triggering a global extinction that wiped out 76% of life on Earth, including all nonavian dinosaurs, pterosaurs and most marine reptiles. Scientists recently pinpointed the season of the disaster and linked it to springtime in the Northern Hemisphere, after analyzing fossilized animals that died minutes after the impact.

They found the fossils at a site called Tanis, where a river once flowed through what is now North Dakota. After the asteroid struck near Mexico's Yucatán Peninsula, the shock sent powerful waves roaring upstream toward Tanis, sweeping up fish and forest creatures and burying them alive under layers of soil. When the water subsided, it left behind an astonishingly well preserved 3D snapshot of destruction, captured within 30 minutes after the asteroid struck, the researchers reported in a new study. Fossils of those filter-feeding fish also held clues about their seasonal growth cycles, hinting that spring had sprung when the fish died and the dinosaurs' reign abruptly ended.

Related: The 5 mass extinction events that shaped the history of Earth

The moment of mass, instantaneous death preserved in Tanis, with broken and splintered fish fossils wrapped around tree branches and strewn in all directions, "was like the worst car crash you've ever seen, frozen in place," said lead study author Melanie During, a doctoral candidate in the Department of Organismal Biology at Uppsala University in Sweden. It was also "the most spectacular deposit I've ever seen in my life," During said at a news conference on Feb. 22.

During excavated Cretaceous fish at Tanis in August 2017, spending two weeks digging out fossils of paddlefish and sturgeons. Fish skeletons — even after fossilizing — retain records of an animal's growth, which depends on seasonal food availability. By mapping these patterns in bone cell growth and density, the scientists hoped to identify which part of the growth cycle the Tanis fish had reached when they died, which could indicate what time of year it was.

The study authors scanned the fossils using synchrotron X-ray imaging, nondestructively imaging and reconstructing the fossils in 3D. They found tiny glass balls called spherules embedded in the fishes' gills; these small spheres fused from ultrahot sediments when the asteroid struck and ejected towering plumes of dirt from the impact crater. Particles flew into Earth's atmosphere and beyond and then rained back down on the planet as glassy beads. 

Other researchers who studied Tanis' Cretaceous death pit calculated that impact spherules would have fallen between 15 and 30 minutes after the asteroid crashed into Earth. Because spherules were in the fishes' gills but had not been swallowed, the fish were likely buried alive immediately after inhaling the glassy beads — within 30 minutes after the asteroid impact, according to the new study.   

Related: Photos: The freakiest-looking fish

Synchrotron scans also revealed signs of cell growth fluctuations in the fossilized bones, taking place over seven years. Much as trees mark the passage of time in the accumulation of rings, which are visible in cross sections of their trunks, fish add layers to their bones as they age, with growth peaking by the end of the summer and then declining over the winter. When the fish died, they were just entering a time of significant bone growth — which coincided with spring, study co-author Dennis Voeten, a research engineer at Uppsala University's Department of Organismal Biology, said at the news conference.

"I think it makes sense to everyone that when a fish eats, its bone grows," During told Live Science in an email. However, seeing this quantified in Cretaceous fossils "is really new and unbelievably informative for future studies," she said.

Records of carbon isotopes, or variations of the element carbon, from one of the fishes further confirmed that the fish died in springtime, the scientists wrote in the study. Like bone growth, "the carbon isotope record shows a distinct cyclic pattern, where high values reflect high productivity of plankton," which was the main food for paddlefish, said study co-author Jeroen van der Lubbe, an assistant professor in the Department of Earth Sciences at the Vrije Universiteit Amsterdam in the Netherlands. Plankton abundance is typically highest in summer; the isotope analysis showed that plankton productivity hadn't yet peaked for the year, so the researchers concluded that the fish perished in the spring, van der Lubbe said at the news conference.

The timing of the asteroid impact likely had far-reaching consequences, with some species on Earth being better equipped to weather the disaster simply because of what season it was in their part of the world, the researchers reported. 

Organisms in the Northern Hemisphere, where spring was warming things up, were likely just emerging and were primed for growth and reproduction after the cold winter months. They would have been exposed and had fewer resources, having already depleted whatever stored reserves helped them survive the winter. A springtime ecosystem could therefore have been more vulnerable to the immediate effects of the impact than plants and animals in the Southern Hemisphere that were hunkering down for winter, During said.

"After the impact, a sudden cooling of unknown duration took place — which, of course, had its own influence on the extinction pattern," During said. "Nevertheless, it is clear that the organismal groups that did not survive that catastrophic spring/autumn would not have been around to fight in the subsequent nuclear winter to begin with." 

The findings were published online Wednesday (Feb. 23) in the journal Nature.

Originally published on Live Science.

Researchers have uncovered the earliest example of a flower bud in a 164 million-year-old plant fossil in China. The discovery firmly pushes back the emergence of flowering plants into the Jurassic period, between 145 million and 201 million years ago. 

The fossil, which was uncovered in the Inner Mongolia region of China, is 1.7 inches (4.2 centimeters) long and 0.8 inches (2 cm) wide. It contains a stem, a leafy branch, a bulbous fruit and a tiny flower bud around 3 square millimeters in size. The researchers have named the new species Florigerminis jurassica.

There are two main types of plants: flowering plants, known as angiosperms, and non-flowering plants, known as gymnosperms. The flower bud and fruit in the fossil are both clear indicators that F. jurassica was an angiosperm and not a gymnosperm, which was the dominant plant type during the Jurassic period. Until now, fossil evidence has shown that angiosperms did not arise until the Cretaceous period, between 66 million and 145 million years ago, but the new fossil is the most convincing evidence yet that this was not the case. 

Related: 10 coolest non-dinosaur fossils unearthed in 2021

"Many paleobotanists are surprised [by the fossil], as it is quite different from what is stated in books," senior author Xin Wang, a researcher at Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (NIGPAS), told Live Science in an email. "But I am not so surprised," he added.

The new fossil is not the oldest example of a fossilized flower to ever be discovered. In 2018, in a study published in eLife, researchers described 174 million-year-old flowers from a plant in the genus Nanjinganthus, also found in China, Live Science previously reported. 

However, some researchers have questioned whether Nanjinganthus can truly be considered an angiosperm because the flowers were not complex enough to distinguish them from leafy structures seen in gymnosperms, ScienceAlert reported. Flowers are also extremely delicate and hard to fossilize, which can make it hard to tell them apart from other plant material, Wang said.

But the flower bud and fruit in the new fossil prove without a doubt that F. jurassica was definitely an angiosperm, he said. The fossil, therefore, "underscores the presence of angiosperms in the Jurassic and demands a rethinking of angiosperm evolution," the researchers wrote in a statement. 

Wang believes that several other known plant genera from the Jurassic period, including Nanjinganthus, Juraherba, Yuhania, Jurafructus, Xingxueanthus and Schmeissneria, could also potentially be angiosperms, but he says there is no way to tell for sure without fossil evidence. Until now, scientists had just assumed those genera were gymnosperms because they arose in the Jurassic.

However, if angiosperms were present during the Jurassic, they would have been very uncommon compared to gymnosperms and geographically isolated, which makes finding similarly well-preserved examples of other flower buds very unlikely, he said. 

Alternatively, it is also possible that F. jurassica may be one of the very first evolutionary links between older angiosperm-like plants, such as Nanjinganthus, and more recent true angiosperms found in the Cretaceous period, Wang said.

The study was published online Jan. 6 in the journal of the Geological Society of London. 

Originally published on Live Science.

The years following the asteroid impact that wiped out non-avian dinosaurs were dark times — literally. Soot from raging wildfires filled the sky and blocked the sun, directly contributing to the wave of extinctions that followed, new research has found.

After the asteroid struck, around 66 million years ago, the cataclysm extinguished many forms of life instantly. But the impact also caused environmental changes leading to mass extinctions that played out over time. One such extinction trigger may have been the dense clouds of ash and particles that spewed into the atmosphere and spread over the planet, which would have enveloped parts of Earth in darkness that could have persisted for up to two years. 

During that time photosynthesis would have failed, leading to ecosystem collapse. And even after sunlight returned, this decline could have persisted for decades more, according to research presented Dec. 16 at the annual meeting of the American Geophysical Union (AGU), held in New Orleans and online. 

Related: Wipeout: History's most mysterious extinctions

The Cretaceous period (145 million to 66 million years ago) ended with a bang when an asteroid traveling at approximately 27,000 mph (43,000 km/h) slammed into Earth. It measured about 7.5 miles (12 kilometers) in diameter, and left behind a scar known as the Chicxulub crater, which lies underwater in the Gulf of Mexico near the Yucatán Peninsula and spans at least 90 miles (150 km) in diameter. The impact eventually snuffed out at least 75% of life on Earth, including all non-avian dinosaurs (the lineage that produced modern birds is the only branch of the dinosaur family tree that weathered the extinction).

Clouds of pulverized rock and sulfuric acid from the crash would have darkened skies, cooled global temperatures, produced acid rain and sparked wildfires, Live Science previously reported. Scientists first proposed the post-asteroid "nuclear winter scenario" in the 1980s; this hypothesis suggested that darkness played a part in the mass extinctions after the Cretaceous impact, said Peter Roopnarine, a curator of geology in the Department of Invertebrate Zoology and Geology at California Academy of Sciences, and a presenter at the AGU meeting.

However, it's only in the past decade or so that researchers developed models showing how that darkness may have impacted life, Roopnarine told Live Science in an email.

"The common thinking now is that global wildfires would have been the main source of fine soot that would have been suspended into the upper atmosphere," Roopnarine said. "The concentration of soot within the first several days to weeks of the fires would have been high enough to reduce the amount of incoming sunlight to a level low enough to prevent photosynthesis."

Dark days

For the research presented at the AGU conference, scientists modeled the effects of long-term darkness by reconstructing ecological communities that would have existed at the time of the asteroid impact. They used 300 species known from the Hell Creek Formation, a fossil-rich expanse of shale and sandstone that dates to the latter part of the Cretaceous and extends over parts of Montana, North Dakota, South Dakota and Wyoming.  

"We focused on that region because the fossil record is well-sampled and well-understood ecologically, so we could reconstruct the paleocommunity reliably," Roopnarine said.

They then created simulations that exposed their communities to periods of darkness lasting from between 100 and 700 days, to see which intervals would produce the rate of vertebrate extinction that was preserved in the fossil record — about 73%, according to the presentation. The onset of post-impact darkness would have been rapid, reaching its maximum in just a few weeks, Roopnarine said in the email.

The researchers found that ecosystems could recover after a period of darkness that lasted up to 150 days. But after 200 days, that same community reached a critical tipping point, where "some species went extinct and patterns of dominance shifted," the scientists reported. In the simulations where darkness lasted for the maximum duration, extinctions spiked dramatically. During a darkness interval of 650 to 700 days, extinction levels reached 65% to 81%, suggesting that the Hell Creek communities experienced about two years of darkness, according to the models.

"Conditions varied across the globe because of atmospheric flow and temperature variation, but we estimated that the darkness could have persisted in the Hell Creek area for up to two years," Roopnarine said, adding that these findings are preliminary and 

Once an ecosystem reached that tipping point, it could eventually rebound with a new distribution of species; however, that process would have taken decades, the researchers found. Extended stimulations of Hell Creek communities that went dark for 700 days showed that after the darkness lifted, it took 40 years for conditions in the ecosystem to start to rebound, the scientists reported at the conference.

Originally published on Live Science.

Earth has not always been upright. Turns out, the planet's crust tipped on its side and back again around 84 million years ago, in a phenomenon that researchers have dubbed a "cosmic yo-yo." 

The actual name for the tipping is true polar wander (TPW), which occurs when the outer layers of a planet or moon move around its core, tilting the crust relative to the object's axis. Some researchers had previously predicted that TPW occurred on Earth late in the Cretaceous period, between 145 million and 66 million years ago, but that was hotly debated, according to a statement by the researchers.

However, the new study strongly suggests TPW did occur on Earth. Researchers mapped the ancient movement of Earth's crust by looking at magnetic-field data trapped inside ancient fossilized bacteria. They found that the planet tilted 12 degrees relative to its axis around 84 million years ago, before fully returning to its original position over the next 5 million years. 

Related: 10 out-of-this-world images of Earth taken by Landsat satellites

"This observation represents the most recent large-scale TPW documented and challenges the notion that the [Earth's] spin axis has been largely stable over the past 100 million years," the researchers wrote in their paper, published online June 15 in the journal Nature Communications. 

Cosmic yo-yo 

Earth is made out of four main layers: the solid inner core, the liquid outer core, the mantle and the crust. During TPW, the entire planet would appear turned over on its side, but in reality only the outermost layers have moved. 

"Imagine looking at Earth from space, TPW would look like the Earth tipping on its side," co-author Joe Kirschvink, a geobiologist at the Tokyo Institute of Technology in Japan and a professor at the California Institute of Technology, said in the statement. "What's actually happening is that the whole rocky shell of the planet [the mantle and crust] is rotating around the liquid outer core."

Individual pieces of Earth's outermost layers are constantly moving and changing as tectonic plates collide together and subduct underneath one another; but during TPW, the outer layers move together as a single unit.

As a result, the tilt in Earth's crust would not have resulted in any major tectonic activity or drastic changes to major ecosystems. Instead, it would have been a gradual process that would not have impacted the dinosaurs and other living things walking around on the surface.

Earth's electromagnetic field would have been static during the TPW because it is created by the liquid inner core, which would have stayed in place. So rather than the magnetic poles moving, it is the geographic poles that start to wander. 

Fossilized magnets 

To test if Earth did undergo TPW during the Cretaceous, the researchers turned to magnetic minerals within limestone deposits in Italy. 

"These Italian sedimentary rocks turn out to be special and very reliable because the magnetic minerals are actually fossils of bacteria that formed chains of the mineral magnetite," co-author Sarah Slotznick, a geobiologist at Dartmouth College in New Hampshire, said in the statement. 

Magnetite is a highly magnetic form of iron-oxide. Some types of bacteria can create chains of tiny magnetite crystals, which naturally orient with Earth's magnetic field at the time of their creation. When these particular bacteria died and were fossilized during the period of TPW, these magnetite chains got locked in place. 

Because Earth's crust moved during TPW, and not its magnetic field, these magnetic fossils (which remained in surface layers of the planet) revealed how much the crust moved relative to Earth's magnetic field over time. The team found that Earth's crust moved a total of almost 25 degrees over a period of 5 million years.

The researchers believe that their findings now settle the question of whether Earth had a TPW during the Cretaceous. 

"It is so refreshing to see this study with its abundant and beautiful paleomagnetic data," Richard Gordon, a geophysicist at Rice University in Houston who was not involved in the study, said in the statement.

Originally published on Live Science.

About 80 million years ago, when dinosaurs walked the Earth, an 18-foot-long (5 meters) sea monster called a mosasaur cruised the ancient ocean that once covered western Kansas, snagging prey with its slender, tooth-lined snout.

Paleontologists discovered the fossil of this beast in the 1970s, but they had difficulty classifying it, so it ended up stored with other mosasaur specimens in the Platecarpus genus, at Fort Hays State University's Sternberg Museum of Natural History (FHSM) in Kansas.

Recently, researchers revisited the enigmatic fossil — pieces of a skull, jaw and a few bones from behind the head — and found that the reptile didn't belong in the Platecarpus genus. Rather, it was a close relative of a rare mosasaur species known from just one specimen, scientists reported in a new study. 

Related: Image gallery: Ancient monsters of the sea

The newly described species, formerly known as specimen FHSM VP-5515 and now named Ectenosaurus everhartorum, is the second known species in the Ectenosaurus genus. The only other species is Ectenosaurus clidastoides, which was described in 1967, according to the study.

E. everhartorum's head was about 2 feet (0.6 m) long, and like E. clidastoides, E. everhartorum had a snout that was narrow and elongated compared with those of other mosasaurs, said study co-author Takuya Konishi, a vertebrate paleontologist and assistant professor at the University of Cincinnati.

"It's a kind of skinny snout for agile, speedy snapping of fish, rather than biting into something hard like turtle shells," Konishi told Live Science. The narrowness of the jaw and of a bone at the top of the head hinted that VP-5515 belonged in the Ectenosaurus genus, even though the fossil was about 500,000 to 1 million years younger than the E. clidastoides specimen, Konishi said.

But in some ways, the skull wasn't Ectenosaurus-like at all. For example, it lacked a bony bump at the end of its snout. The snout on VP-5515 was also shorter than the one on E. clidastoides, according to the study.

"We knew it was a new species, but we didn't know if it was an Ectenosaurus or not," Konishi said. "To answer that puzzle, we were eventually able to find another feature where the jaw joint was, at the back end of the lower jaw." There, the researchers detected a small notch that didn't appear in any mosasaur species — except one.

"That little depression turned out to be a newly discovered consistent feature for the genus Ectenosaurus," Konishi said. "You have this Ectenosaurus united by the little notch at the end of the lower jaw, but then it's consistently different at the level of the species from the generic type — that is to say, the first species assigned to the genus."

One lingering question about Ectenosaurus is why this genus is so poorly represented among mosasaur fossils from western Kansas. To date, paleontologists have uncovered more than 1,800 mosasaur specimens at the site of the former inland sea. But for now, the entire Ectenosaurus genus is represented by just two fossils — one for each species. 

"That's very strange," Konishi told Live Science. "Why is it so rare for a mosasaur, where you have hundreds of Platecarpus from the same locality? Does that mean they were living near shore, or were they living farther south or farther north? We just don't know."

The findings were published Aug. 26 in the Canadian Journal of Earth Sciences.

Originally published on Live Science.

An enormous triceratops nicknamed "Big John" is expected to fetch big bucks on the auction block in France, in October. 

The skeleton, which is more than 66 million years old and is approximately 60% complete, is the largest triceratops ever found. It measures about 26 feet (8 meters) long; the skull, which is 75% complete, is 6.6 feet (2 m) wide. 

French auction house Giquello will display the massive fossil to the public from Sept. 16 to Oct. 15 at 13 Rue des Archives in Paris, Giquello representatives said in a statement. Then, on Oct. 18, the giant dinosaur fossil will make its debut appearance at the Parisian auction house Hôtel Drouot, where it will be auctioned on Oct. 21 to the highest bidder as part of Giquello's "Naturalia" auction. Big John is expected to fetch between $1.4 million and $1.8 million (1.2 million and 1.5 million euros), according to the statement.

Related: Tiny & old: Images of 'triceratops' ancestors

Frilled, tri-horned triceratops inhabited North America about 67 million to 65 million years ago during the Cretaceous period (145.5 million to about 65.5 million years ago). Big John lived in what is now South Dakota on an island continent called Laramidia, which formed during the latter part of the Cretaceous when a shallow sea flooded North America's central region. 

The fossil was discovered in 2014 by paleontologist Walter W. Stein, owner of the independent commercial paleontology company PaleoAdventures in South Dakota. Stein excavated the skeleton from the Hell Creek Formation, an ancient flood plain and a rich fossil site that spans parts of Montana, North Dakota, South Dakota and Wyoming. Much of the formation is on state and federal lands, according to the University of California Museum of Paleontology at Berkeley. 

Millions of years ago, Big John died and was covered by thick mud, which enabled the bones to fossilize. A preserved notch in his collarbone suggests that the triceratops was wounded during violent combat, possibly during a tussle with another triceratops over mates or territory, according to the statement. 

The other triceratops may have fared even worse in that battle: Big John's two largest horns each measure nearly 4 feet (1.1 m) long and almost 1 foot (30 centimeters) wide at the base, and can withstand about 16 tons (14.5 metric tons) of pressure, representatives said. 

Other dinosaur fossils have commanded even heftier price tags at auction than Big John is likely to. In October 2020, a 67 million-year-old T. rex named Stan sold at auction for a record-breaking $31.8 million, making it the most expensive fossil of all time. Sales of high-profile fossils have raised concerns among paleontologists that museums and other scientific institutions will be outbid on valuable specimens, which will then disappear into private collections and be lost to researchers, Live Science previously reported.

Originally published on Live Science.

About 110 million years ago in what is now Australia, a flying "dragon" dominated the skies. With an estimated 23-foot (7 meters) wingspan, it was the continent's biggest pterosaur, new research finds.

Pterosaur fossils are rare in Australia; fewer than 20 specimens have been described since paleontologists found the continent's first pterosaur bones about two decades ago. Scientists identified the newfound species, Thapunngaka shawi, from a fossilized piece of a lower jaw found at a site in North West Queensland dating to the Cretaceous period (about 145.5 million to 65.5 million years ago).  

T. shawi's skull would have measured over 3 feet (1 m) long, and its mouth would have been crammed with approximately 40 teeth, making the extinct reptile "the closest thing we have to a real life dragon," study lead author Tim Richards, a doctoral candidate and researcher in The University of Queensland (UQ) Vertebrate Palaeontology and Biomechanics Lab, said in a statement.

Related: Photos of pterosaurs: Flight in the age of dinosaurs

The pterosaur's genus name, "Thapunngaka," comes from one of the languages spoken by the Indigenous people of the Wanamara Nation, who live where the fossil was discovered. The name incorporates "thapun [ta-BOON'] and ngaka [NGA'-ga]," which are "the Wanamara words for 'spear' and 'mouth,' respectively," the researchers wrote. "Shawi," the species name, is a nod to the man who found the fossil, an amateur prospector named Len Shaw. 

"So the name means 'Shaw's spear mouth,'" the scientists wrote in the study.

The spear-mouthed pterosaur had a crest on the underside of its lower jaw, and its upper jaw was likely crested, too, according to the study. Toothed pterosaurs called anhanguerians had such skull crests, and the researchers classified T. shawi as part of that group. 

"These crests probably played a role in the flight dynamics of these creatures," study co-author Steven Salisbury, a senior lecturer in the UQ School of Biological Sciences, said in the statement.

The scientists also counted tooth sockets in the jaw fragment, and determined that the pterosaur would have had at least 26 teeth in its lower jaw and up to 40 teeth in total.

When T. shawi was alive, about 60% of the Australian continent would have been underwater, covered by shallow seas. Though the T. shawi fossil was a rare find, paleontologists had previously found numerous fossils of marine invertebrates — such as mollusks, snails and ammonites — at the Queensland site, as well as fossils of vertebrates, like sharks and other fishes, and plesiosaurs and ichthyosaurs (extinct marine reptiles). While the flying Cretaceous "dragon" T. shawi probably wasn't big enough to carry off a plesiosaur, it likely was a swift and deadly predator, swooping down to scoop up fish from the water or to nab small prey on land, Richards said in the statement. 

"It would have cast a great shadow over some quivering little dinosaur that wouldn't have heard it until it was too late," Richards said. "This thing would have been quite savage."

The findings were published Aug. 9 in the Journal of Vertebrate Paleontology.

Originally published on Live Science.

A bizarre group of raptor-like dinosaurs, known as alvarezsaurs, drastically shrank around 100 million years ago, transforming from ostrich-size predators that hunted early mammals and baby dinos to ant-eaters the size of a chicken, according to paleontologists. 

Alvarezsaurs were slender theropods — a diverse group of two-legged dinosaurs with hollow bones and three-toed limbs, including Tyrannosaurus rex and Velociraptor — that may have been feathered. There are 21 confirmed species of alvarezsaurs dating from between the late Jurassic period around 160 million years ago and the end of the Cretaceous period around 66 million years ago. 

In a new study, paleontologists examining the fossils of these dinos have revealed that the group massively decreased in size between 110 million and 85 million years ago. Before this, alvarezsaurs weighed between 22 and 154 pounds (10 and 70 kilograms), but they quickly slimmed down to under 11 pounds (5 kg), with one species shrinking to just 0.3 pounds (0.15 kg).

Related: 7 surprising dinosaur facts 

"Size reduction is very uncommon in Cretaceous theropod dinosaurs," lead author Zichuan Qin, a doctoral student at the University of Bristol in the U.K. and the Institute of Vertebrate Paleontology and Paleoanthropology in China, told Live Science. At this time, most other dinosaurs were getting bigger, and the only other group to decrease in size was the theropod lineage that eventually evolved into modern-day birds, he added. 

The researchers suspect that a significant shift in global ecosystems during the Cretaceous period may be behind the alvarezsaurs' shift in diet and rapid miniaturization.

Comparing species 

Until now, paleontologists had been baffled by the remarkable size differences within alvarezsaur species. The largest species, Bonapartenykus ultimus, is over 460 times heavier than the smallest species, Parvicursor remotus, Qin said.

To figure out why there was such a size spread, the researchers compared the size and age of alvarezsaur specimens they had collected, as well as data from other studies, while taking extra care to make sure that specimens were fully, or close to fully, grown. They relied on growth rings within the bones (sort of like tree rings) to estimate the maturity of their specimens.

"Including juveniles in the dataset would deeply influence the accuracy of the results," Qin said. 

The results revealed a threefold decrease in the average body size of alvarezsaurs over a period of around 25 million years, which is a "quick jump" in terms of evolutionary time, Qin said.

As alvarezsaurs got smaller, they also displayed physiological changes, the most notable of which was that their arms became much shorter and they lost all but one of their fingers. This arm change was likely the result of a change in diet. Bigger species had long arms with fingers and claws that would have allowed them to grab at prey they were chasing, while smaller species would have been suited to jabbing and poking at social insects, such as ants and termites, inside their mounds.

The researchers also found that as alvarezsaurs got smaller their growth rate significantly decreased, meaning they would have taken longer to reach maximum size, Qin said. But the growth rates also varied significantly between these smaller species, he added.

Switching tactics 

Next, the researchers turned their attention to what may have caused this rapid shrinking. Their main theory is that the miniaturization was the result of an equally rapid change in the dinosaurs' ecosystem.

Around the same time as alvarezsaurs started shrinking, Earth experienced what is now known as the Cretaceous Terrestrial Revolution. During this time, between 125 million and 80 million years ago, there was a massive increase in the diversity and abundance of flowering plants.

With such a bloom in these plants, social insects like ants, termites and bees would have flourished, creating a new ecological niche that was most likely exploited by alvarezsaurs that shrunk down to take advantage of the new food, Qin said. This new ecological niche also led to the emergence of more alvarezsaur species than ever before, he added. 

"At that time, this ant-eating niche was rare, which gave Alvarezsaurus a huge space to explore," Qin said.

The study was published online July 6 in the journal Current Biology.

Originally published on Live Science.

A fossil locked in a piece of amber dating to about 99 million years ago belongs to a newfound and highly bizarre species of extinct lizard. The fossil also helped scientists revise the lineage of another amber-locked discovery, also dating to that part of the Cretaceous period (145.5 million to 65.5 million years ago), that was originally thought to be the smallest known ancient bird.

When researchers described the hummingbird-size Oculudentavis khaungraae in March 2020, it was hailed as the tiniest dinosaur ever found (birds are a lineage of dinosaurs that survive to the present). But the specimen had a number of features that hinted it might be a lizard, and the journal retracted the study in July 2020, Live Science previously reported. 

The new find, dubbed Oculudentavis naga, is a more complete specimen than O. khaungraae, having an intact skull and part of its spine and shoulders. After analyzing O. naga bone by bone, scientists determined that despite having some birdlike features it was a lizard — albeit a very strange lizard — and so was its "bird" cousin, according to a new study.

Related: In photos: Amber preserves Cretaceous lizards

Amber fossils form after an animal or plant becomes trapped in sticky resin from a coniferous tree. Over time, as the resin hardens into amber around the organic matter, it seals the organism away from oxygen and bacteria, and protects it from decay and environmental wear, according to the University of California Museum of Paleontology in Berkeley. 

These fossils often retain soft tissue, such as the feathered wings torn from a bird, a feathered dinosaur's tail and an ancient lizard's tongue. Amber can also preserve rare instances of animal behavior — a 41 million-year-old insect sex romp, for instance.

Many amber fossils dating to the Cretaceous come from Kachin province in Myanmar — both Oculudentavis specimens came from the province's Aung Bar mine, according to the new study. Indigenous people there managed the amber deposits and mining prior to 2017, but after the Myanmar military seized control of the mines, their operations displaced thousands and are linked to human rights abuses, New Scientist reported in 2019. 

However, the O. naga amber specimen was acquired legally and exported from Myanmar prior to 2017 by study co-author Adolf Peretti, a gemologist with GRS Gemresearch Swisslab, the scientists reported.

Birdlike lizard or lizardlike bird?

O. naga's skull measures just 0.6 inches (14.2 millimeters) in length, and its long, tapering snout tipped with elongated nostrils is more like a bird's beak than a lizard's nose, according to the study published Monday (June 14) in the journal Current Biology.

When compared side-by-side with O. khaungraae (which measures 0.7 inches or 17.3 mm), the O. naga skull looks quite different: Its crown is flatter; it has a broader snout; and the eye opening, though large for a lizard, isn't quite as big as O. khaungraae's. Yet the animals are more closely related than those preserved skull shapes suggest, and that relationship — and their identification as lizards — became clearer when researchers X-ray scanned the skulls, created digital 3D models and examined them one bone at a time, said study co-author Edward Stanley, an associate scientist at the Florida Museum of Natural History in Gainesville, and director of the museum's Digital Discovery and Dissemination (3D) imaging lab.

Both specimens had teeth with long roots that were attached to the jaw. Known as pleurodont dentition, these teeth are common in lizards and "don't look like dinosaur teeth," which are seated in sockets, Stanley told Live Science. 

"There's a bone at the back of the jaw called a quadrate that attaches the lower jaw to the top of the skull and the braincase — that's also very lizardlike in both specimens," Stanley said. "The roof of the mouth, while unusual for a lizard, is much more lizardlike than birdlike," Stanley added. A skull bone that's shaped like a hockey stick, called a jugal, ticked yet another box on the lizard list of features for both animals, the scientists wrote in the study.

Yet O. naga and O. khaungraae also both had "a strange-looking bone" directly in front of the eye socket that was unlike anything seen in most lizards, Stanley said. 

"The fact that a lizard skull — the first specimen, the holotype of Oculudentavis khaungraae — could be misidentified as a bird is a good indication that this reptile is a really unusual one," said lead study author Arnau Bolet, a research fellow at the Autonomous University of Barcelona's Miquel Crusafont Catalan Institute of Paleontology.

Deformed by time

One explanation for why the specimens look so different from each other — and why O. khaungraae had a more birdlike appearance, with a rounder skull and pointier snout — could be that the skulls were deformed by fossilization. As O. naga was a more complete specimen, it provided the scientists with a clearer picture of the bones. After scanning the skulls with computed X-ray tomography (CT), the researchers digitally reversed deformation in the models, revealing that the two species were more similar than they first appeared.

"We used CT data to try to isolate all the individual bones piece by piece, so we really broke it down into its component parts," Stanley said. "When you do that, it becomes a lot clearer: Not only is this thing a lizard, but these things are very closely-related weird lizards."

O. naga was less laterally deformed than O. khaungraee, making it "less prone to interpretation as a bird," Bolet told Live Science in an email. Nevertheless, the fossil "still shows that Oculudentavis deviates from the standard lizard morphology in some aspects, rendering it a highly interesting animal," Bolet added. "They show that there is much to be learned about the evolution of species in the past, and give us a glimpse of the way different groups — in this case, lizards — diversified to occupy different roles in the ecosystem."

While Oculudentavis' status as a bizarre lizard genus is now clearer, its exact position on the lizard family tree is still unknown, the scientists reported. But with all the CT data now available for free at MorphoSource, an online repository for 3D scientific data, other researchers will have the opportunity to try to solve this intriguing evolutionary puzzle.

"You can 3D-print this model or use a computer simulation to test things like bite force, or jaw angle — that might tell a little more about what this animal was doing in life. You can isolate the inner ear of the specimen, that might tell you about the type of environment it lived in, whether it lived up in trees or on the ground," Stanley said. "We're keen to work on it, and we're keen for other people to work on it as well."

Originally published on Live Science.

Paleontologists in Madagascar recently discovered an exceptionally well-preserved fossil of a new and extinct species of turtle, dating back to the late Cretaceous Period, which began around 100 million years ago. The newly discovered species would have had a frog-like face and eaten by sucking in mouthfuls of prey-filled water.

The ancient turtle was a freshwater species endemic to Madagascar, with a shell length of around 10 inches (25 centimeters). It had a flattened skull, rounded mouth and large tongue bones, all of which would have made it a great suction feeder and given it an amphibian-like appearance. In a new study describing the species, the researchers named it Sahonachelys mailakavava, which means "quick-mouthed frog turtle" in Malagasy, the language spoken by Indiginous people of Madagascar.

Researchers unearthed the turtle's fossil in 2015 while searching for the remains of dinosaurs and crocodiles at a site on the island with a history of such finds. While removing the overburden — the typically bare layers of sediment above fossil-rich layers — the team was surprised to find bone fragments from a turtle's shell and eventually recovered an almost intact skeleton.

Related: Sea science: 7 bizarre facts about the ocean 

"The specimen is absolutely beautiful and certainly one of the best-preserved late Cretaceous turtles known from all southern continents," lead author Walter Joyce, a paleontologist at the University of Fribourg in Switzerland, told Live Science. "In all regards, this is an exceptionally rare find."

The researchers are unsure how far back the quick-mouthed frog turtle may have emerged or when and why it went extinct; but the new species "likely survived the big extinction event that killed the dinosaurs" and brought the Cretaceous Period to an end around 66 million years ago, Joyce said.

Suction feeders 

Quick-mouthed frog turtles were most likely suction feeders, the researchers said.

"This is a specialized mode of underwater feeding, during which the animal quickly opens its mouth and expands its throat to quasi-inhale a large volume of water, including the desired prey item," which would have included plankton, tadpoles and fish larvae, Joyce said.

Its flattened skull, mouth shape and delicate jaws are all telltale signs that this turtle used suction for feeding. "Suction feeders need to quickly create a large circular opening through which they suck water," Joyce said. "As the prey items are transported directly into the esophagus, suction feeders do not have strong jaws, as they do not bite."

The turtle also had enlarged tongue bones for its size, which suggests it had strong muscles to allow the quick expansion of its throat, Joyce said. 

Convergent evolution 

The quick-mouthed frog turtles belonged to the Pelomedusoidea family, which includes living species such as South American and Madagascan river turtles. "Although the group is not particularly diverse today, its fossil record shows that the group nearly conquered all landmasses in the past and was much more diverse," Joyce said.

The quick-mouthed frog turtle was "likely the first Pelomedusoid" to have evolved as a suction feeder "to such an extreme," Joyce said. There are several modern-day turtle species that suction feed, most of which belong to the family Chelidae and evolved separately from the quick-mouthed frog turtle. 

When Joyce first saw the skull, he thought it belonged to a Chelid, he said. "The shell, however, clearly showed that it is a Pelomedusoid." This is evidence of convergent evolution and means Chelids and Pelomedusoids, which are distantly related, have each evolved this ability independently of one another, Joyce said.  

"It highlights that distantly related animals will converge upon the same shape when adapting to similar lifestyles," Joyce said.

The study was published online May 5 in the journal Royal Society Open Science.

Originally published on Live Science.

Could you run faster than a T. rex? According to new research, you might be able to outpace one by walking.

In the movie "Jurassic Park" (Warner Bros, 1993), a carful of terrified people famously tries to escape a loping T. rex, but science quickly threw shade at the movie beast and demonstrated that the king of tyrannosaurs wouldn't have been fast enough to run down a jeep. Now, researchers have slowed down the big dinosaur even more. 

New simulations based on tail movement showed that T. rex wasn't even a quick walker. In fact, its preferred walking speed clocked in at just under 3 mph (5 km/h), about half the speed of earlier estimates. To put that into perspective, that's about the average walking speed for a human, according to the British Heart Foundation. 

Related: Image gallery: The life of T. rex

Tyrannosaurus rex, the biggest of all carnivorous dinosaurs, lived in what is now the western United States, from about 66 million to 68 million years ago toward the end of the Cretaceous period, and they likely numbered in the billions. 

An adult T. rex would have measured about 40 feet (12 meters) long, stood 12 feet (3.6 m) tall and weighed about 11,000 to 15,500 pounds (5,000 to 7,000 kilograms) on average, according to the American Museum of Natural History in New York City. The heaviest known T. rex, a hefty specimen found in Saskatchewan, Canada, and nicknamed "Scotty," weighed in at a whopping 19,555 pounds (8,870 kg), Live Science previously reported.

But how fast could such a big animal move? Previously, researchers answered that question by looking at T. rex's mass and hip height, sometimes incorporating stride length from preserved trackways. Those estimates placed a T. rex's walking speed roughly between 4.5 and 6.7 mph (7.2 and 10.8 km/h), about as fast as a mediocre human runner. 

For the new investigation, rather than focusing on T. rex's legs, scientists instead explored the role played by the vertical movement of the tyrannosaur's tail, said Pasha van Bijlert, a master's candidate studying paleo-biomechanics at the Free University of Amsterdam, and the lead author of the new study on T. rex walking speed. 

"Dinosaur tails were vital to the way they moved around, in multiple ways," van Bijlert told Live Science in an email. "Not only does it serve as a counter balance, the tail also produces a lot of the required force to move the body forward. It does this through two large tail muscles — the caudofemoral muscles — that pull the legs backwards during each step." 

Passive and active

In the bipedal (two-legged) T. rex, the tail would have been passively suspended in the air but also actively engaged and naturally swaying up and down during walking. "This combination — passive suspension while active in locomotion — is unique to dinosaurs; there are no animals alive today with this feature," van Bijlert explained. "Because of this, we were highly intrigued by its role in the way that T. rex would have walked."

As a T. rex tail sways, it stores and releases energy through stretchy ligaments. When the rhythm of a swinging tail achieves resonance — "the biggest movement response with the least amount of effort" — that rhythm is known as the tail's "natural frequency," van Bijlert said. The natural frequency in a T. rex tail would then indicate the animal's step frequency during unhurried walking, the researchers wrote in the new study, published online April 21 in the journal Royal Society Open Science.

Related: In images: A new look at T. rex and its relatives

Standing in as the researchers' model T. rex was an adult specimen known as "Trix," in the collection of the Naturalis Biodiversity Center in Leiden, the Netherlands. The study authors scanned and modeled Trix's tail bones, referencing marks on the well-preserved vertebrae that showed where ligaments attached. From this digital bone and ligament reconstruction, they created a biomechanical model of the tail.

"The tail model gives you a likely step frequency/rhythm for T. rex, but you also need to know how much distance it travels with each step," van Bijlert said. To find that, the scientists took the step length of a tyrannosaur that was slightly smaller than Trix, scaling it up to Trix's size. They determined that Trix's step length would be 6.2 feet (1.9 m), then calculated walking speed by multiplying the step frequency with step length. 

"Our baseline model had a preferred walking speed of 2.86 mph [4.6 km/h]," which was significantly slower than earlier estimates of walking speed, van Bijlert said in the email. "Depending on some of the assumptions regarding the ligaments and how the vertebrae rotate, you get slightly slower or faster speeds (1.79 to 3.67 mph [2.88 to 5.9 km/h]), but across the board, they're all slower than earlier estimates," he said. 

Covering new ground

However, there is still some uncertainty to this range, as it focuses on the up-and-down tail movements, "and muscles — as well as side-to-side motions — are not considered," John Hutchinson, a professor of evolutionary biomechanics at The Royal Veterinary College in Hertfordshire, United Kingdom, told Live Science in an email.

"No one in their right mind has thought that dinosaurs had perfectly rigid tails (up/down or side/side), but it has been a neglected topic for locomotion," said Hutchinson, who was not involved in the new research. "So, this study covers some new ground in a clever way with an original model." 

The new estimate also reflects "a heavy emphasis on elastic storage," the study authors wrote, and the storage capacity of tyrannosaur tails could be lower than the model suggests, Hutchinson added. Nevertheless, this flexible tail model "would be useful to integrate with and compare with other approaches in the future," he said.

As for T. rex's next steps, the study authors want to incorporate their flexible tail into models of a running T. rex, van Bijlert said. Maximum running speed for a T. rex is thought to be in the range of 10 to 25 mph (16 to 40 km/h), according to Hutchinson. Biomechanics researchers have long proposed that T. rex's maximum running speed would be limited by the strength of its bones, because the animal was so heavy. However, a flexible tail could change that by acting as a shock damper during running, "allowing it to run faster without breaking its bones," van Bijlert said. 

"We'd also like to apply our method to more species, because that might reveal interesting evolutionary adaptations in the tail's role in locomotion," he added. 

Originally published on Live Science.

Mosasaurus was a ferocious predator in the ancient oceans of the Cretaceous period (145.5 million to 65.5 million years ago). While dinosaurs dominated the land, Mosasaurus used its long tail and stumpy, paddle-like limbs to cruise through the water, devouring all kinds of prey with its massive jaws and sharp, cone-shaped teeth. 

Mosasaurus is one genus, or group of species, out of dozens that made up a diverse family of marine reptiles called mosasaurs. The mosasaurs ruled the ocean in the late Cretaceous period. They were not sea dinosaurs, but a separate group of reptiles, more closely related to modern snakes and lizards, according to the Philip J. Currie Dinosaur Museum. 

Mosasaurs went extinct 65.5 million years ago in the same mass extinction event that wiped out the dinosaurs, Live Science previously reported. A Mosasaurus species has since been fictionally resurrected on the big screen, most notably in the 2015 movie blockbuster "Jurassic World," increasing the profile of this mighty group of marine reptiles. 

Related: T-Rex of the seas: A mosasaur gallery

How big was Mosasaurus and other mosasaurs?

Mosasaurus species are among the largest members of the mosasaur family, according to the Philip J. Currie Dinosaur Museum. One of the biggest specimens ever found was identified as Mosasaurus hoffmanni and was estimated to be about 56 feet (17 meters) long in life, according to a 2014 study published in the journal Proceedings of the Zoological Institute RAS. Not all mosasaurs were giants though. Some species, such as Xenodens calminechari, were only about the size of a porpoise, Live Science previously reported. 

The biggest Mosasaurus would have been comparable in size to the mighty megalodon — a giant shark that dominated oceans in the middle Miocene and Pliocene epochs (15.9 million to 2.6 million years ago), long after the mosasaurs went extinct 65.5 million years ago. Megalodons could have reached up to 49 to 59 feet (15 to 18 meters) long, according to the Natural History Museum (NHM) in London. Neither of these predators, however, were ever as big as the modern blue whale, which can reach up to 110 feet (34 meters) long and is the biggest known animal to have ever existed. 

Related: Newfound ancient 'sea monster' is largest yet from Antarctica 

What did Mosasaurs eat, and how did they catch it?

Mosasaurs were the ocean's most dominant predator at the end of the Cretaceous period and lived across the world's oceans. Large mosasaurs would have likely eaten almost any kind of prey they were able to catch, including fish, sharks, sea birds and even other mosasaurs, according to the U.S. National Park Service. These mosasaurs were apex predators and could be compared to modern orcas, while other mosasaur species were more specialized feeders and adapted to eat shellfish, like modern sea otters, Live Science previously reported.

Occasionally, mosasaur fossils were preserved with their stomach contents intact, which helps paleontologists learn more about their hunting strategies. For example, paleontologists in Canada uncovered a specimen from the species Mosasaurus missouriensis with large fish bones inside it, according to National Geographic. The fish was larger than the mosasaur's head, and the placement of the bones suggested the mosasaur had devoured its prey piece by piece. 

Related: Full belly fossil! 'Sea monster' had 3 others in its gut 

In another fossil find, a juvenile Mosasaurus was found in the stomach of another mosasaur species, Prognathodon kianda. The fossil, from the Smithsonian National Museum of Natural History (NMNH), demonstrates that even the largest mosasaur species could be preyed upon. In fact, Mosasaurus hoffmanni fossils have been uncovered with severely broken and healed jaws that indicate they led a violent or dangerous lifestyle, according to a 1995 study published in the journal Philosophical Transactions of the Royal Society B.

Mosasaurus probably hunted in fairly deep waters, but would not have traveled too far from the shore, according to the NMNH.

Mosasaurs may have started out swimming through the water like a snake or an eel, but mosasaur tails changed over time. The animals evolved to have a shark-like tail to propel themselves through the water. They may also have been capable of a powerful breaststroke, using their paddle-like forelimbs to assist in sudden bursts of speed to catch prey.

How accurate was “Jurassic World” mosasaur?

The movie "Jurassic World" (2015) features an iconic shot of a giant Mosasaurus rocketing out of the water to snatch a dangling shark. This big-screen depiction of the ancient sea monster made several other appearances in the "Jurassic World" series, but experts didn't consider the depiction scientifically accurate. 

The real Mosasaurus species were simply not that big, paleontologists told Live Science shortly after "Jurassic World" was released in 2015. The creature in the film is about twice the size of the largest known mosasaur fossil, according to ReBecca Hunt-Foster, a paleontologist at the Bureau of Land Management Canyon Country District, and John Foster, the director of the Museum of Moab. 

Kenneth Lacovara, then a professor of paleontology and geology at Drexel University, also acknowledged the marine reptile was too large but gave the film "kudos" for including an accurate depiction of the mosasaur's palatal teeth — a specialized second set of teeth in the animal's upper mouth, similar to those in some snakes and lizards that hold prey in place and prevent its escape. 

According to Philip J. Currie Dinosaur Museum, the movie mosasaur's movement is also inaccurate, based on a dated interpretation of Mosasaurus swimming like eels or snakes.

Related: Ancient Antarctic sea monster may have laid this football-size egg

What happened to Mosasaurs?

The mosasaurs disappeared from the fossil record alongside non-avian dinosaurs 65.5 million years ago, after a giant asteroid crashed into Earth at the end of the Cretaceous period. The rich marine ecosystems that mosasaurs inhabited and depended upon for food collapsed after the asteroid strike, according to a 2005 study in the Netherlands Journal of Geosciences. This collapse caused all mosasaurs to die out, never to return. 

The role of dominant ocean predator was once held by marine reptiles that resembled modern dolphins, known as ichthyosaurs. Those animals were succeeded by the plesiosaurs, which were then replaced by the mosasaurs, according to the Naranjo Museum of Natural History. After mosasaurs disappeared, crocodilians increased in numbers and took over the role of large marine predators, according to the Netherlands Journal of Geosciences study.

Related: Dinosaur-killing asteroid triggered mile-high tsunami that spread through Earth's oceans

Additional resources

• Ancient battle left 'sea monster' with tooth stuck in its face
• Adorable newborn sea monster from the dinosaur age discovered in Kansas 
• Ancient 'sea monster' swam like a shark 

Tarantulas, everyone's favorite hairy spiders, are found worldwide, inhabiting all continents except Antarctica. But how did they become so widespread? Females rarely leave their burrows, spiderlings stick close to where they hatch, and mature males only travel when they're searching for a mate. 

To answer this question, researchers went looking for the origins of the tarantula group more than 100 million years ago, building a tarantula family tree based on molecular clues from existing databases of spiders' transcriptomes — the protein-coding portion of the genome, found in ribonucleic acid, or RNA. 

Once they created the tree, they mapped it to a timeline of spider fossils, to estimate when — and where — tarantulas appeared and dispersed.

Related: In photos: Tarantulas strut their stuff

The scientists discovered that tarantulas first emerged during the Cretaceous period in what is now the Americas. But at the time, the Americas were part of the massive supercontinent Gondwana. Ancient tarantula relatives, even if they were homebodies like tarantulas today, likely spread across the joined landmasses, dispersing from the Americas into Africa, Australia and India. Then, after Gondwana broke apart, India separated from Madagascar and collided with Asia — and brought the hairy spiders to that continent, too, he researchers reported.

There are only two known tarantula fossils, both preserved in amber: One is from Mexico, and is thought to be around 16 million years old, and the other is from Myanmar and is about 100 million years old, the study authors reported. Because tarantula fossils are so rare, the researchers also collected data from related mygalomorphs — the arachnid group that includes tarantulas and other big, ground-dwelling spiders — that are better represented in the fossil record than are tarantulas. 

After constructing a family tree for tarantulas from transcriptome data, representing 29 tarantula species and 18 other mygalomorphs, the scientists time-calibrated the tree using data from fossils. This enabled the researchers to calculate the ages of tarantula lineages, and to approximate when the ancestors of modern tarantulas spread over the world.

Tarantula timeline

According to this new timeline, tarantulas first appeared in the Americas about 120 million years ago. There, the spiders that were ancestors to Africa's tarantulas emerged around 112 million to 108 million years ago. By about 108 million years ago, tarantulas were established in what is now India. India separated from Madagascar between 95 million and 84 million years ago, and drifted toward Asia; that slow-motion collision, which began between 58 million and 35 million years ago, brought tarantulas to the Asian continent.

However, before that happened, India's tarantulas diverged into two lineages with different lifestyles: One group of tarantulas was predominantly tree-dwellers, and the other mostly preferred life in burrows. Both lineages eventually spread into Asia, but the arboreal group (Ornithoctoninae, also known as "Earth tigers") did so 20 million years after their burrowing cousins.

This second, later wave of tarantula dispersal into Asia suggests that the spiders were able to fill ecological niches and adapt to new habitats more effectively than once thought.

"Previously, we did not consider tarantulas to be good dispersers," lead study author Saoirse Foley, an evolutionary biologist at Carnegie Mellon University in Pittsburgh, said in a statement. "While continental drift certainly played its part in their history, the two Asian colonization events encourage us to reconsider this narrative," Foley said.

The findings were published online April 6 in the journal PeerJ.

Originally published on Live Science.

A 66 million-year-old fossilized lung from a previously unknown species of ancient fish, as large as a great white shark, has recently been uncovered in Morocco. 

Researchers believe the fish was a much larger member of the coelacanths, an Order of fish nicknamed the 'living fossils that were thought to be extinct until a live specimen was found in 1938. Given the size of the newfound lung, this particular coelacanth would have been 17 feet (5.2 meters) long, according to the researchers.

The fossilized lung was part of a large slab, uncovered in phosphate beds in Oued Zem in Morocco, which contained several other bones belonging to pterosaurs. The bones confirm that the coelacanth dates back to the end of the Cretaceous period 66 million years ago, just before the dinosaurs became extinct.

Related: T. rex of the seas: A mosasaur gallery

"It is absolutely enormous; it's a giant coelacanth, in a place we have never found them before" said study co-author David Martill, a paleontologist at the University of Portsmouth in England. 

The new discovery sheds light on one of the most mysterious fish groups to ever swim in the oceans, but it also raises questions about what happened to them.

A lucky find 

A private pterosaur collector in London bought the fossil slab from a seller in Morocco and originally mistook the fossilized fish lung as part of a pterodactyl skull. But on closer inspection, he was unsure, so he contacted Martill to get his professional opinion. 

"He sent me a bunch of pictures, and I really didn't know what it was," Martill told Live Science. "But I really didn't think it was part of the pterosaur." 

However, after visiting the fossil slab in person, Martill knew exactly what he was looking at. "I realized that instead of being one bone, it was actually hundreds of very thin sheets of bone," Martill said.

The fossil lung was somewhat barrel-shaped, but instead of the staves — the wooden planks that make up a barrel — lined up along the barrel, they were wrapped around it and overlapping.

"There's only one species that has a bone structure like that, and that's the coelacanth fish," Martill said. "They actually wrap their lung in this bony sheath, it's a very unusual structure."

Initially disappointed, the collector allowed Martill to separate the lung from the rest of the slab so it could be properly analyzed.

After discovering the fossilized lung, Martill teamed up with Brazlillian paleontologist Paulo Brito, a world leading expert in coelacanth lungs, from the State University of Rio de Janeiro. Brito confirmed Martill's suspicions and was "astonished" at the size of the specimen, according to a statement from the University of Portsmouth. 

Previously discovered ancient coelacanths lived in rivers and had bodies extending between 10 and 13 feet (3 and 4 meters) in length; but the new unnamed species, which is thought to have lived in the open ocean, would have been much bigger. Modern-day coelacanths are smaller than both and reach around 6 feet (1.8 m) long.

"The coelacanth body plan has been pretty constant for the last few hundred million years," Martill said. "This one is just much bigger."

The collector has since donated the lung to the Department of Geology at Hassan II University of Casablanca in Morocco.

Mysterious end

One of the biggest mysteries surrounding the fossilized lung is where the rest of the coelacanth's massive body ended up. Martill's leading theory is that one of the large reptilian marine predators that dominated the Cretaceous oceans — such as plesiosaurs and mosasaurs — may have eaten it

"Coelacanths were slow-swimming fishes; this massive version would have been easy prey for these big predators," Martill said. 

The researchers also found damage on the lung, which also suggests the fish was bitten by one of these massive predators. 

Plesiosaurs and mosasaurs would have also regurgitated up large bones from their meals, like modern-day lizards do, which could explain why the lung ended up isolated with other bones from different animals. It would also explain why other coelacanths haven't been found in the area, as the fish may have been eaten hundreds of miles away and then regurgitated much later.

However, there is no way to prove that it died in this way.

"We haven't written about this in the paper, because the evidence is really tenuous," Martill said. "It's a good story but it's only one possibility."

What happened to the rest of the coelacanths is also a mystery. They completely disappear from the fossil record at the end of the Cretaceous period, which is what originally led scientists to think they were extinct. But live coelacanths found within the last century prove that at least one species managed to survive. 

"We keep finding coelacanths up until the end of the Cretaceous, and then they just disappear," Martill said. "This is one of the last coelacanths before what we call the pseudoextinction."

It is possible that these giant coelacanths could still secretly roam the unexplored pockets of the deep sea today. But although he hopes this might be the case, Martill admitted: "the evidence of this happening isn't good."

The study was published online Feb. 15 in the journal Cretaceous Research.

Originally published on Live Science.

A tree in an ancient forest sits covered in moss, lichens and craggy bark — when suddenly, a chunk of that bark begins to scuttle around. 

But it's not the bark that's scurrying; it's a bizarre little creature called Stegastochlidus saraemcheana, a newfound genus and species of cylindrical bark beetle. Scientists recovered the creature, which looks like a walking scrub brush, from 100-million-year-old amber collected in the Hukawng Valley of northern Myanmar. That dates the beetle back to the Cretaceous, the period between 145.5 million and 65.5 million years ago.

"The beetle must have spent its life among moss, lichens and fungi, either attached to tree trunks or on the forest floor," study co-author George Poinar Jr., a paleobiologist and entomologist at Oregon State University, said in a statement. "He is hiding under a spectacular camouflage of his own making, allowing him to blend into a mossy background." 

This "spectacular camouflage" earned the beetle its genus name, from the Greek words "stegastos," meaning covered, and "chlidos," meaning ornament, the authors wrote. (The textbook "Composition of Scientific Words" (Washington, 1954) defines the similar word "chlidon" as meaning "bracelet, anklet or ornament.") 

Related: Animal camo: Can you find the animals hiding out in these images? 

This jagged ornamentation makes the beetle look less like an insect and more like a  chunk of tree bark. In their paper, published Dec. 15 in the journal Biosis: Biological Systems, the authors helpfully point out which end of the peculiar bug is its head and which is its body. 

From a top view, the head juts off from the tubular body as a rounded, tuft-like structure covered in spikes. Two segmented antennae extend from the head and end in a club-like shape. From a side view, the head sits at one end of the beetle, with the forelegs and midlegs just behind it. The hindlegs sit slightly farther back on the body, in front of the beetle's cylindrical abdomen. 

The whole bug measures just 0.17 inches (4.2 millimeters) long, but it crams more than 100 spike-like structures onto its back and head. These spikes likely helped the beetle blend in with moss, lichens and fungi, the authors wrote.

"A close association with fungi is indicated by strands of fungal spores, known as conidia, attached to the beetle's cuticle, or outer covering," Poinar said in the statement. A pair of parasitic mites were also found latched onto the beetle by their mouthparts, the authors noted. While snacking on the beetle some 100 million years ago, these mites also became trapped in amber.

The beetle's pointed mouthparts hint at a carnivorous diet, so the bug likely preyed on other invertebrates, the authors noted. With such a narrow body, the beetle could easily slip into galleries — vertical structures built in wood by other beetles — and potentially gobble up the pupae and larvae housed there.

Originally published on Live Science. 

About 125 million years ago, two dinosaurs that had likely dozed off in an underground burrow drew their last breaths before they were buried alive, possibly by a volcanic eruption, a new study finds. 

The pristinely preserved remains of these two nearly 4-foot-long (1.1 meters) reptiles looked so serene that researchers named the newly discovered species Changmiania liaoningensis, which means "eternal sleeper from Liaoning" in Chinese.

"It is tentatively hypothesized that both Changmiania liaoningensis specimens were suddenly entrapped in a collapsed underground burrow while they were resting, which would explain their perfect lifelike postures" and why their remains weren't damaged by the elements or by scavengers, the researchers wrote in the study.

Related: Photos: Newfound tyrannosaur had nearly 3-inch-long teeth

Chinese farmers in Liaoning province in northeastern China discovered the two specimens, which are now housed at the Paleontological Museum of Liaoning. An international team of paleontologists from China, Argentina and Belgium then set to work studying the "eternal sleeper's" unique anatomy.

Their analysis revealed that C. liaoningensis was an early ornithopod, a type of herbivorous dinosaur that walked on two legs, such as Iguanodon and the hadrosaurs, or duck-billed dinosaurs. Judging by its powerful hind legs and long, stiff tail, it's a good bet that C. liaoningensis was a swift runner, the researchers said.

Moreover, C. liaoningensis was likely an expert burrower, which is uncommon among dinosaurs but not without precedent. 

"Certain characteristics of the skeleton suggest that Changmiania could dig burrows, much like rabbits do today," study senior researcher Pascal Godefroit, a paleontologist at the Royal Belgian Institute of Natural Sciences, said in a statement. "Its neck and forearms are very short but robust, its shoulder blades are characteristic of burrowing vertebrates and the top of its snout is shaped like a shovel."

The Lujiatun Beds, where these fossils were found, are well known for extraordinary fossils — specimens thought to have been preserved by an ancient volcanic eruption, like a Cretaceous period version of Pompeii (the Roman city that was destroyed but eerily preserved by an eruption from Mount Vesuvius in A.D. 79). Other 3D fossils from this site provide evidence that some dinosaurs were devoted parents, and that mammals the size of opossums once feasted on tiny dinosaurs.

In the case of the two C. liaoningensis dinosaurs, "it can be hypothesized that the burrows containing the Changmiania skeletons collapsed during the debris flow episode; we can alternatively imagine that the Changmiania specimens dug their burrow in unstable reworked volcanic material just after the debris flow," the researchers wrote in the study, adding that "those explanations, of course, remain pure speculations," because the fossils were excavated by farmers, not scientists, so certain details about the location weren't studied.

Still, the burrowing dinosaur's lifelike posture "implies that the animals were rapidly entombed while they were still alive," although it's possible the sediment covered them soon after death, the researchers wrote in the study. 

The C. liaoningensis fossils reveal other hints about their lives. For instance, unlike another dinosaur immortalized in the Lujiatun Beds — Mei long, a bird-like troodontid dinosaur that slept with its tail curled under its neck — C. liaoningensis slept with its tail stretched out. That's because the "eternal sleeper" had a "rather rigid" tail with limited flexibility, the researchers wrote in the study. "Curling its tail under its neck in a Mei-like style was therefore likely impossible for Changmiania."

Another fossilized clue includes a cluster of a dozen small pebbles found near the stomach area of one of the C. liaoningensis individuals. These pebbles may have been gastroliths, or rocks that some animals swallow on purpose to help grind food during digestion, the researchers said.

The study was published online Sept. 8 in the journal PeerJ.

Originally published on Live Science.

An enormous Cretaceous crocodile relative hunted dinosaurs, ripping them apart using powerful jaws lined with teeth "the size of bananas," researchers say.

Known as Deinosuchus, which means "terrible crocodile" in Greek, this lineage of semiaquatic reptiles certainly lived up to its name. They were among the biggest predators in their watery North American habitats, where they lived between 75 million and 82 million years ago. And with bodies at least 33 feet (10 meters) long, they could subdue just about any animal that wandered within reach — including dinosaurs. 

Paleontologists had previously identified three species of the terror crocs. But some experts argued that fossil evidence defining the species was incomplete, and that the three species could just be one that ranged across the continent. Scientists recently re-evaluated fossils of so-called terror crocodiles, combining existing species and describing a new one, Deinosuchus schwimmeri, in a new study.

Related: Crocs & dinos: See images of 25 amazing ancient beasts

In addition to having banana-size teeth, the newly described D. schwimmeri was "a bizarre, monstrous predator," said lead study author Adam Cossette, an assistant professor in the New York Institute of Technology College of Osteopathic Medicine at Arkansas State University. Cossette and his colleagues described the new species by sampling fossils from across North America, and by evaluating new terror croc fossils from western Texas, according to the study. 

"Until now, the complete animal was unknown," Cossette said in a statement. The species name honors paleontologist David Schwimmer, a professor at Columbus State University in Georgia (not to be confused with the actor David Schwimmer, who played a paleontologist from the American Museum of Natural History in New York City, in the TV show "Friends").

Deinosuchus are crocodylians — the group that includes modern alligators, crocodiles and gharials — and despite the name "terrible crocodile," the Deinosuchus lineage was more closely related to alligators, the researchers determined. They also found that the species D. rugosus was likely misidentified. D. rugosus fossils (of which there are very few) likely came from two other species — D. riograndensis or D. schwimmeri — both of which were described later but boasted more complete sets of fossils. 

The species status of the terror croc D. hatcheri, also based on scant and fragmented fossil evidence, is also questionable, the authors reported.  

D. schwimmeri inhabited North America's eastern shores and the coastal Atlantic, while D. riograndensis and D. hatcheri lived in the West; at the time, the Western Interior Seaway geographically separated the eastern and western species, the study authors wrote.

But no matter the species, "Deinosuchus was a giant that must have terrorized dinosaurs that came to the water's edge to drink," Cossette said.

While Deinosuchus shared many features with its crocodylian relatives, a couple of peculiarities set them apart. Their broad, elongated heads ended in a bulbous snout — a shape that is unique among this group of reptiles, according to the study. At the end of the snout are two large vents, which are also unique to Deinosuchus. 

Scientists have yet to uncover the function of the apertures and snout shape, though they may be linked to thermoregulation, and may have helped the terror crocs keep cool, according to the study. 

"It was a strange animal," said study co-author Christopher Brochu, a paleontologist and professor in the department of Earth and Environmental Sciences at the University of Iowa. The findings were published online Aug. 10 in the Journal of Vertebrate Paleontology.

Originally published on Live Science.

Around 99 million years ago, a juvenile cockroach met a hellish fate. It was snapped up by the jaws of a Cretaceous hell ant, a fierce predator with long, curving mandibles that swept up toward the top of the ant's head. 

Just moments later, the ant and roach were trapped in sticky sap that eventually turned to amber, providing scientists with a first glimpse of how the weird-faced ants trapped prey. 

The profile of a hell ant, with exaggerated upward-facing jaws that arc like the Grim Reaper's scythe, is unlike that of any ant alive today. Adding to the facial weirdness is a hell ant's horn, which comes in a variety of shapes in this ant group, known as Haidomyrmecine.  

Researchers had long suspected that hell ants swung their prominent mandibles upward to catch their prey, unlike modern ants that snap their jaws together horizontally. In the piece of Cretaceous amber from Myanmar, scientists found the first confirmation of this hunting technique.

Related: Photos: Ancient ants & termites locked in amber

Hell ants lived during the Cretaceous period (about 145.5 million to 65.5 million years ago), and are known from amber deposits in Myanmar, France and Canada spanning 100 million to 78 million years ago, said evolutionary biologist Phillip Barden, an assistant professor in the Department of Biological Sciences at the New Jersey Institute of Technology. Barden and his colleagues described the amber-embedded hell ant in a new study, published online today (Aug. 6) in the journal Current Biology.

Scientists described the first hell ant about a century ago, and have since identified 16 species — all of whom have elongated mandibles and horns. 

In the amber, the mandibles of the hell ant Ceratomyrmex ellenbergeri hug the roach nymph, Caputoraptor elegans, from below, pinning it against the horn on the ant's head. Finding this rare example of fossilized predation was astonishing — but also vindicating, Barden told Live Science.

"When we first started working on hell ants in 2011 to 2012, it looked like the only way they could have fed was by moving their mouth parts vertically," Barden said. At the time, the notion was "a little contentious," but this little hell ant showed their hypothesis was correct, he said.

The researchers also digitally modeled the heads of Ceratomyrmex and other hell ants in 3D, comparing them to both  modern and extinct ants. Their analysis of the evolutionary relationships between the groups confirmed that hell ants were among the earliest known ants, according to the study.

Social digestion

The amber-trapped hell ant never got to eat the roach. However, Barden offered some diabolical possibilities for how that meal may have unfolded. 

"First thing would probably be that the ant would have stung the prey to paralyze it," he said. And how would it have eaten the roach? "We originally thought that all the hell ants would have pierced their prey and drunk the hemolymph, which is like insect blood," Barden said. However, while some hell ant species have horns that are reinforced for piercing, Ceratomyrmex's horn was holding the nymph in place but not piercing it.

The best potential explanation, Barden told Live Science, comes from the feeding habits of a modern ant from Madagascar called the Dracula ant (Adetomyrma venatrix), which also has oddly-shaped mandibles.

"They have these highly specialized mouthparts that are so exaggerated they can't feed themselves," Barden explained. "Instead, they feed the prey to their own larvae — and the larvae have unspecialized mouthparts, so they can chew normally."

Once the larvae are fed, what happens next truly seems like a scene from hell. Adult ants pierce the larvae's sides and they drink the hemolymph of their own offspring and siblings, a charming practice called non-destructive cannibalism, Barden said.

"Basically, they use their own siblings and offspring as a social digestive system," he said. "We don't have direct evidence that's the case here, but that could be something that's going on."

Originally published on Live Science.

A hefty, 10-foot-long (3 meters) crocodile relative had an odd way of getting around 120 million years ago in what is now South Korea. The huge beast walked on its two hind legs like a T. rex, researchers said after analyzing footprints left behind by the reptile. 

There are no known fossilized bones of this strange crocodile, but dozens of its up to 120 million year-old footprints, including one with skin impressions, are preserved in stone.

"For the first time, we have proof that some of the giant crocodiles of the Cretaceous were bipedal and really designed like the carnivorous dinosaurs," study co-researcher Martin Lockley, professor emeritus of geology at the University of Colorado Denver, told Live Science.

Related: Photos: Dinosaur tracks reveal Australia's 'Jurassic Park'

Researchers found the fossilized footprints ahead of a construction project. Researchers named it the Sacheon Jahye-ri tracksite, as it's west of Sacheon City in South Gyeongsang Province.

The track marks are big, up to 9.5 inches (24 centimeters) long, the researchers said. The crocodile also likely "had legs about the same height as human adult legs," study senior researcher Anthony Romilio, a paleontologist at the University of Queensland in Australia, said in a statement. 

After Korean researchers transferred the trackways to a lab, they invited Lockley to look at the impressions in November 2019. Initially, the team thought that these prints might belong to a giant pterosaur, but the instant Lockley saw them, he said he knew they were from a crocodile relative. 

Previously, Lockley had studied crocodile prints from the Jurassic period (199 million to 145 million years ago). The crocodile that left those prints was much smaller — its tracks were about 1 inch, or 2.5 centimeters long — and it walked on all fours. Even so, those prints were remarkably similar to the newly discovered ones, he said.

This realization triggered another memory; Lockley and his colleagues had published a study in 2012 in the journal Ichnos on what they thought were giant pterosaur tracks from the Cretaceous period of Korea. At the time, however, they knew something was weird about the tracks, so they called them "enigmatic." Looking back, Lockley realized that just like the newfound tracks, the enigmatic prints are most likely from a two-legged crocodile. 

Working together, the team found myriad clues that the newfound trackway belonged to a crocodile and not a pterosaur. For example, pterosaurs likely used their wings while walking, meaning they walked on all fours. But no handprints (or wing prints, for that matter) were found. In addition, the skin impression found on a heel print resembled that of a crocodile, Lockley said. Moreover, the prints had robust digits and impressions of pads and joints that looked just like those from a crocodile, he said.

That said, it's understandable that the researchers initially thought these trackways belonged to giant pterosaurs. "Typical crocodiles walk in a squat stance and create trackways that are wide," study lead researcher Kyung Soo Kim, a paleoecologist at the Chinju National University of Education in South Korea, said in the statement. "Oddly, our trackways are very narrow looking — more like a crocodile balancing on a tight-rope." 

"When [the footprints were] combined with the lack of any tail-drag marks, it became clear that these creatures were moving bipedally," Kim said. 

The team named the newfound fossil prints Batrachopus grandis. (Trace fossils, such as fossilized trackways and burrows, are given scientific names, just as animals are.) 

During the lower Cretaceous, the track site was a lake surrounded by muddy ground, "which made for making good tracks," Lockley told Live Science. It's difficult to say how these prints were preserved, but perhaps the creature left the prints in wet mud just before the lake retreated, allowing the prints to dry and harden. When the water level rose again, mud and fine silt could have covered and preserved the tracks, Lockley said.

Or, maybe the mud was soft and soupy, like warm ice cream, but the ground under the "ice cream" was hard, he said. The crocodile could have squished through the muck and left an impression on the hard ground underneath, which would have been instantly buried and preserved by the "ice cream" when the animal lifted up its foot, Lockley said. 

The study was published online yesterday (June 11) in the journal Scientific Reports. 

• Photos: Giant long-necked dinosaurs walked on water
• Photos: Analyzing an Amazing, Amphibious Dinosaur
• Photos: Dinosaurs sloshed around ancient lagoon

Originally published on Live Science.

Tyrannosaurus rex wasn’t born the massive beast known for ripping prey to shreds. A paleontologist has found the beast goes through 21 distinct growth stages as it develops from a wee, slender tot to a full-grown, massive dinosaur king. And the two most important stages on its growth chart occurred when T. rex became a teenager and around its 18th birthday.

The study — the most comprehensive to date focused on T. rex growth — also revealed: The male and female skeletons look exactly alike; the controversial Nanotyrannus is not a separate species; and adult T. rex's size and weight are not predictive of its age. 

Paleontologist Thomas Carr spent about three years studying 44 different T. rex skeletons being stored at natural history museums across North America. It was a laborious but rewarding scrutiny of the hypercarnivore, which lived from about 67 million to 65 million years ago, at the end of the Cretaceous period, he said. 

"I just love the way these animals look," Carr, a vertebrate paleontologist and an associate professor of biology at Carthage College in Wisconsin, told Live Science. "I'm in love with their faces. I think they're beautiful. And I want to understand every little [developmental] change that happens. I want to see through their eyes, if that's at all possible."

Related: Gory guts: Photos of a T. rex autopsy

The dinosaurs in the study ranged in age from a 2-year-old at the Natural History Museum of Los Angeles County to the 28-year-old Sue at the Field Museum in Chicago. 

Every time Carr examined a different T. rex, he assessed up to 1,850 features on it, such as skull length, chronological age (as determined from the growth rings in certain bones) and the presence of certain bumps on the bones. 

After studying the 44 T. rexes, Carr excluded 13 "wildcards" because they didn't fit in with the rest of the data. But even with 31 T. rexes, "this work is clearly the most massive, time-intensive effort to understand the growth of the tyrant king," said Lindsay Zanno, head of paleontology at the North Carolina Museum of Natural Sciences, who wasn't involved in the study.

For instance, the data revealed that the two most important stages happened when T. rex roared into its teenage years and later, when it lumbered into young adulthood. 

The first change happened when T. rex exited its preteen years. Just before turning 13, "when T. rex was young, the skull was very long and low, [with] fairly narrow teeth," Carr said. "These animals are about 21 feet [6.4 meters] long." The sleek juveniles "don't look like adults at all. In fact, juveniles have been mistaken as a different species called Nanotyrannus, but they're really young rexes," he said. 

Then, sometime between age 13 and 15 (there are no specimens that died at age 14), "everything changes," Carr said. "In a span of two years, the entire head and jaw deepen, the teeth get thick and basically they now look like T. rexes."

The second monumental change happened just after that, around the time of their 18th birthday. "That's when T. rex is heavier than 3 tons [2.7 metric tons]. And that's important because no other tyrannosaurs are that heavy," Carr said. "By the time T. rex is between 15 and 18 years old and reaches its giant size — it leaves all other tyrannosaurs in the dust in terms of size."

It was already known that T. rex outpaced its fellow tyrannosaurs in terms of growth, "achieving colossal size by packing on the pounds faster," Zanno told Live Science. "We knew that Tyrannosaurus rex had to morph from baby into a bone-crunching behemoth in just around two decades, but until now, we didn’t have a complete understanding of how this transition occurred."

Related: Photos: Newfound dinosaur had tiny arms, just like T. rex

However, big and heavy T. rexes weren't necessarily older than less robust adults. "For example, one of the least mature adults [known as Scotty] is also the largest and most massive example of the species," Carr wrote in the study. His research puts Scotty in the 23 to 27 age bracket, meaning the dinosaur is younger than Sue.

Carr's data also revealed that T. rex male and female skeletons looked exactly alike, as is true of other dinosaurs. The only known ways to sex a dinosaur are to see if it has eggs inside of it, or to find medullary bone, a special bone tissue found in the long bones of females only when they are pregnant.

Is Nanotyrannus real?

As for the Nanotyrannus controversy, Carr studied the Cleveland skull (the first so-called Nanotyrannus) and the teenage Jane, another Nanotyrannus candidate. Some people think that Nanotyrannus is a type of dwarf tyrannosaur, but many paleontologists think that it's simply a young T. rex. 

According to data gathered on each specimen, these so-called Nanos fit perfectly into the T. rex growth series , Carr said. 

"If they were a separate species, they ought to be sharing a branch and they ought to be on a branch separate from the other T. rex, but they aren't; they're successive," Carr said. In addition, Jane is at a transitional stage between the younger Cleveland skull and the older T. rexes, he said.

"It turns out that Jane actually shows the first indications that the skull is starting to get deep. You don't see that in the Cleveland skull," Carr said. "So, Jane is actually almost like a missing link between the Cleveland skull — a really slender-snouted juvenile — and the subadults and adults that look like normal rexes."

These results jibe with those of another study, published in January in the journal Science Advances, which looked at Jane's bone growth. Jane's bones showed "features characteristic of actively growing juvenile dinosaurs that had not yet entered an exponential phase of growth," the researchers wrote in that study, meaning that Jane was a growing T. rex, not a dwarf dinosaur. 

Nanotyrannus, however, still needs to be investigated further, said Mark Norell, the chair and Macaulay Curator of Paleontology at the American Museum of Natural History in New York City, who was not involved in the research, but has worked with Carr on other studies.

Related: In photos: Montana's dueling dinosaur fossils (including the so-called Nanotyrannus)

Even though Norell said he personally agrees that Nanotyrannus is likely a young T. rex, and even though the Cleveland skull and Jane fit into Carr's T. rex growth series, there are still questions about Nanotyrannus' anatomy, including the length of its forelimbs and the fact that it has more teeth than adult T. rexes do, he said. 

"I don't think the case is open and shut on that animal yet," Norell noted.

Not enough rexes?

Norell questioned some of Carr's other findings, too. That's because even with 31 T. rexes "the sample [size] is still small, especially when you take into account how poorly preserved the specimens are," Norell told Live Science.

A better sample size would have included 25 T. rexes for each age group, Norell said. (Granted, that many T. rexes haven't been found yet, Carr previously told Live Science.) With so few dinosaurs in the study, the assessment that there are 21 growth stages "is a little over-split, especially concerning the sample size," Norell added. Even the lack of sex differences is suspect: "Because of [the] sample size, I don’t think that you can tell either way," Norell said.

Carr defended his work, saying that his method to uncover the T. rex's growth over time "isn't a statistical test that is dependent upon a high sample size. In fact, the sample size of the specimens in my analysis (31) is at the norm, whereas the amount of data (1,850 characters [per dinosaur]) is extraordinarily high for an analysis of this type."

For comparison, in another study, this one co-led by Carr, the researchers analyzed 30 species of tyrannosaur and examined "a mere 386 characters," per specimen to come to the conclusion that T. rex might have been an invasive species from Asia, he said.

If the growth results weren't truly present in the new analysis, "a growth series wouldn't have been recovered in the first place," Carr added. 

The new study was published online June 4 in the journal PeerJ. 

• Photos: Tiny tyrannosaur dinosaur was about as big as T. rex's skull
• In images: A new look at T. rex and its relatives
• Photos: The near-complete Wankel T. rex

Weird, multisided geometric shapes called buckyballs have been discovered in an unexpected place: marine animals that lived 80 million years ago. 

Microscopic forms of buckyballs have been found in molecules within cosmic dust, in gases and in some types of rocks. But researchers were surprised to find them at a much larger scale in fossils of two species of Cretaceous crinoids, which are relatives of modern starfish and sea urchins. The plates on the crinoids' bodies created multifaceted, hollow structures that the scientists identified as buckyballs.

Their discovery is the first evidence that the bizarre buckyball shape occurs naturally at such a large scale, the scientists reported in a new study.

Related: Fabulous fossils: Photos of the earliest animal organs

Buckyballs, short for "Buckminsterfullerenes," are large spherical molecules, that are made up of 60 carbon atoms linked together in pentagons and hexagons, forming a surface like that of a soccer ball. These strange molecules, first discovered in space in 2010, got their name from architect Buckminster Fuller, who popularized a similar structure in the 1940s called a geodesic dome. 

In space, buckyballs exist in gas and in particles. They have also been detected on Earth in gases emitted by burning candles and in certain minerals, according to NASA. However, that distinctive buckyball shape was previously unknown to exist in animals — living or extinct, said study co-author Aaron Hunter, a research fellow at The University of Western Australia's School of Earth Sciences.

"This is the first time we have found such a structure in fossils," Hunter said in a statement.

Crinoids first appeared during the Cambrian period (about 543 million to 490 million years ago). Most crinoid species — also known as sea lilies or feather stars — died during the Permian mass extinction, around 250 million years ago, but some survive to this day. Animals in this group have a goblet-shaped body called a calyx, topped with branching arms. Many of the fossil forms had stemlike structures that anchored them to the seafloor, according to the British Geological Survey.

Dozens of fossils of two species of late-Cretaceous crinoids — Marsupites testudinarius and Uintacrinus socialis — provided scientists with a highly detailed look at the calyxes' hexagonal and pentagonal plates, made of calcium carbonate. The study authors  created a graph that mapped the plates, visualizing how the animals' bodies would have looked in three dimensions.

Overall, the two species share a structurally similar body plan. But U. socialis had a bigger calyx made of numerous small, lightweight plates, each of which had between four and eight sides. The calyx of M. testudinarius, by comparison, had fewer plates with only five or six sides, and these were much larger than the plates on U. socialis.

Both of the crinoids had calyxes that were shaped like buckyballs. "The ball-like structures, able to withstand very heavy loads, formed around them to protect them from the harms of the ocean," Hunter said in the statement.

However, there were critical differences between the two animals, the scientists wrote in the study. M. testudinarius's calyx, with bigger plates of similar shapes, more closely resembled the buckyball carbon molecule. This would have made the calyx stronger and more stable. But U. socialis's calyx was broader with more variation in the number of plate sides, making the calyx more likely to bend and buckle. Its calyx was probably more useful for buoyancy than for protection against predators, the researchers reported.

This highly unusual body structure could have helped crinoids adapt and spread through ocean depths around the world. Yet many questions remain about how their strange buckyball bodies evolved, and why this shape has only been found in two extinct species that vanished between 84 million and 72 million years ago, according to the study.

"It still remains a mystery why these successful structures did not evolve again," Hunter said.

The findings were published in the May issue of the journal Paleontology.

• In photos: Amber preserves Cretaceous lizards
• Photos: Cretaceous 'graveyard' holds a snapshot of the dino-killing asteroid impact
• Image gallery: Ancient monsters of the sea

Originally published on Live Science.

About 70 million years ago, a cousin of Velociraptor got in a brawl with a larger predator that left it with a nasty rib injury. But this dinosaur, a feathered hypercarnivore, lived to tell the tale, as its rib showed signs of healing, a new study finds.

The newfound species, dubbed Dineobellator notohesperus, had another injury; a gash on its sickle-shaped claw that "we hypothesize may have been made by another Dineobellator," said study lead researcher Steven Jasinski, a paleontologist and head of the Paleontology and Geology Section at The State Museum of Pennsylvania.

"If they lived in packs, this [gash] could have been fighting between members, or could have been due to fighting over potential mates," Jasinski told Live Science in an email. "It's also possible this was a fight between two Dineobellator over food, or even one trying to kill another to eat it."

Related: Photos: 7-year-old boy discovers T. rex cousin 

The dinosaur's fossils were discovered in the San Juan Basin of northwestern New Mexico during the summer of 2008. Given the dinosaur's impressive injuries, the scientists named it Dineobellator notohesperus (pronounced "dih NAY oh - BELL a tor" "Noh toh - hes per us"), by combining the Navajo word "Diné" (Navajo people) with the Latin word "bellator" (warrior). Its species name comes from "noto" and "hesper,"  the Greek words for "south" and "west," respectively, in reference to the American Southwest. 

D. notohesperus belongs to the dromaeosaurid family, a group of small to medium-size feathered carnivores, including Velociraptor, that lived during the Cretaceous period (145 million to 65 million years ago). After analyzing the bones, paleontologists determined that D. notohesperus would have measured about 6.5 feet (2 meters) long, about 3 feet (1 m) tall at the hip and weighed about 40-50 lbs. (18-22 kilograms), making it about as heavy as a female poodle. Remarkably, features on its forearm revealed that D. notohesperus is "one of the rare dinosaurs from North America that shows evidence of feathers," Jasinski said. 

D. notohesperus was hypercarnivorous, meaning that it almost exclusively ate meat. If these dinosaurs lived in packs, as evidence of other raptors suggests, it's possible that a pack of these warrior dinosaurs "would have been able to attack and take down prey several times larger than them," Jasinski said. 

The fossils also revealed that D. notohesperus was strong for its size. It had strong muscles on its humerus, or upper arm, and the nearly 4-inch-long (10 centimeters) claws on its hands and feet could have closed strongly around prey, Jasinski said. Its hands would have had "a very strong grip for grasping things," he added. 

Cheetah-like hunter?

The vertebrae near the base of its tail curved inward, suggesting that D. notohesperus had increased agility, which would have helped it hunt prey. 

"Other members of this group of dinosaurs tend to have straight, stiff tails that are reinforced with rod-like features made of bones and tendons," Jasinski said. But the newfound dinosaur appears to have had a highly mobile tail. "If you think of videos of cheetahs pursuing prey like gazelles, their tail tends to stay relatively straight but whip around as the cheetah quickly changes direction. Dineobellator would have had a similar ability to quickly change directions during pursuit," he said. 

However, the assessments of this creature's strength and tail may be premature, said David Evans, chair of vertebrate paleontology and deputy head of the Department of Natural History at Royal Ontario Museum in Canada, who was not involved in the study.

"Ultimately, the specimen is still very fragmentary and leaves a lot of questions, including the strength of the functional inferences in the study," Evans told Live Science in an email. "Although the bones suggest Dineobellator may have had a suite of special adaptations that could be related to predation for instance, the scrappy nature of the fossils makes it difficult to evaluate the significance of the seemingly unique shapes of its bones."

"More complete fossils and comparative functional analyses are needed to more reliably infer the behavior of Dineobellator," Evans said. 

However, the bones do reveal D. notohesperus' roots. Based on the dinosaur's anatomy, "we have determined that Dineobellator is closely related to dromaeosaurids from Asia," meaning that D. notohesperus is a descendant of migrants from Asia, Jasinski said.

The study was published online March 26 in the journal Scientific Reports.

• Gory guts: Photos of a T. rex autopsy
• In images: Tyrannosaur trackways
• Image gallery: Tiny-armed dinosaurs

Originally published on Live Science.

Millions of years ago, a flying reptile as big as an airplane took flight in what is now Canada. 

Now, this enormous species of giant pterosaur — part of a group known as azhdarchids — finally has a name: Cryodrakon boreas, drawing from the ancient Greek words that translate to "cold dragon of the north winds." 

Fossils of Cryodrakon boreas were found decades ago, and were thought to belong to another North American azhdarchid: Quetzalcoatlus, one of the biggest flying animals of all time. But the discovery of additional fossils in recent years told scientists that the fossils represented a newfound species, and the first new species of giant pterosaur found in Canada. 

Based on the size of one enormous neck bone thought to belong to an adult animal, the newly described pterosaur likely had a wingspan extending about 33 feet (10 meters) from tip to tip, making it comparable in size to its monstrous azhdarchid cousin Quetzalcoatlus, researchers reported in a new study.

Related: Photos of Pterosaurs: Flight in the Age of Dinosaurs

All of the Cryodrakon fossils came from Dinosaur Provincial Park in Alberta, and date to approximately 77 million to 74 million years ago during the Cretaceous period (145.5 million to 65.5 million years ago), according to the study.

Azhdarchids lived on all continents except Antarctica and Australia, and are known for having supersize heads, long necks, long legs and large feet, said lead study author David Hone, a senior lecturer and director of the biology program at Queen Mary University in London. But despite this group's massive size, very few fossils of the flying giants remain, Hone told Live Science in an email.

Fossils are typically preserved when animal remains are buried in layers of sediment and locked away from bacteria that break down organic matter. Many of the best-preserved remains from millions of years ago belonged to animals that lived near seas or rivers, and pterosaurs at this time (including Cryodrakon) mostly lived inland, Hone explained. 

"And their bones are insanely thin, so they are very rare," he added. "We're lucky we have as much good material as we do." 

What might C. boreas have looked like in life? Paleoartist David Maas illustrated the pterosaur with a distinctive pattern of red and white that will likely be immediately recognizable to any Canadian. Viewed from above with its wings at full spread, the markings across Cryodrakon's back and wingtips strongly resemble the Canadian flag, down to the iconic maple leaf in the center.

This was a "fun" artistic choice, as there's no fossilized evidence of the animal's colors or patterns, Hone told Live Science in the email. Nevertheless, "it's actually a plausible colour scheme," he added. 

"It's nothing ridiculous or impossible based on what we know about the colours of large living birds," Hone said.

The findings were published online Sept. 9 in the Journal of Vertebrate Paleontology.

• Photos: Ancient Pterosaur Eggs & Fossils Uncovered in China
• In Images: A Butterfly-Headed Winged Reptile
• In Photos: Bizarre 'Bat Dinosaur' Discovered in China

Originally published on Live Science.

About 120 million years ago, a small dinosaur gulped down a lizard, swallowing the reptile whole. The wee lizard's story might have ended there, but the dinosaur died soon after and was preserved as a fossil. Millions of years later, paleontologists discovered the scaly meal in the dinosaur's belly.

Scientists found the lizard when they examined the fossil of a feathered dinosaur named Microraptor zhaoianus, a small carnivore from the early Cretaceous period (145.5 million to 65.5 million years ago) in what is now northeastern China. In Microraptor's abdomen was a near-complete skeleton that the researchers identified as a previously unknown lizard species.

This "exceptional specimen" paints a clearer picture of the animal diversity in this region during the Cretaceous, and it hints at what was on the menu for dinosaur predators like Microraptor, the scientists reported in a new study. [In Photos: Amber Preserves Cretaceous Lizards]

Microraptor belongs to the theropod (meat-eating) dinosaur group known as the dromaeosaurids — small to medium-size bird-like dinosaurs — which also includes Velociraptor and Deinonychus. It had flight feathers on its front and back limbs, and it could likely glide or even fly, according to the study.

The fossilized lizard's skeleton was still whole and nearly complete, and it appeared to belong to a juvenile. Its position inside the dinosaur's gut showed that it was gulped down head first, "consistent with feeding behavior in extant carnivorous lizards and birds," the study authors wrote.

They dubbed the ingested lizard Indrasaurus wangi: The species name honors paleontologist Yuan Wang, director of the Paleozoological Museum of China, and Indrasaurus refers to a legend from ancient Indian texts about the deity Indra, who was swallowed whole by a dragon.

Close examination of the lizard's teeth revealed that they were widely spaced, short-crowned and nearly square. They were unlike the teeth in other Cretaceous lizards, and their unusual shape suggests that the lizard may have had a diet that differed from that of its close relatives, the scientists said in the study.

Microraptor and its lizard lunch provide a rare glimpse of direct interactions between predators and prey in ecosystems that vanished millions of years ago. They were found alongside other Microraptor fossils that hold the remains of mammals, fish and birds in their bellies, according to the study.

Using these fossils and others from more than two dozen animal groups, the researchers reconstructed a food web showing who ate whom in the Jehol Biota; this site in Liaoning, China — where Microraptor was discovered in 2005 — holds a diverse array of exceptionally preserved fossils dating from 133 million to 120 million years ago.

The findings were published online July 11 in the journal Current Biology.

• Tiny Dino: Reconstructing Microraptor's Black Feathers
• Images: Dinosaurs That Learned to Fly
• Image Gallery: 25 Amazing Ancient Beasts

Originally published on Live Science.

Baby pterosaurs — flying reptiles that lived alongside dinosaurs — were probably able to spread their leathery wings and fly shortly after emerging from their eggs, scientists reported in a new study.

Preserved eggs and embryos from Argentina and China suggested that pterosaur babies, or "flaplings," according to the researchers, had skeletons and wing membranes that were already flight-capable when the flaplings were freshly hatched.

Previously, other researchers had suggested that hatchling pterosaurs' bones and wings weren't developed enough for the animals to take to the air. But this new analysis presents a greater range of developmental stages, delivering a more complete picture of the embryos as they grew. This suggests that embryos described in earlier studies were not yet fully developed; by the time the pterosaurs were ready to hatch, they would be ready to flap away on their own, the authors wrote in the new study. [Photos of Pterosaurs: Flight in the Age of Dinosaurs]

Prior conclusions about flapling flight were also shaped by comparisons with modern animals that fly: birds and bats. Neither of those groups can fly as newborns, so it was thought that newly hatched pterosaurs probably couldn't fly either, lead study author David Unwin, an associate professor with the School of Museum Studies at the University of Leicester in the United Kingdom, told Live Science in an email.

Unwin and co-author D. Charles Deeming, a principal lecturer with the School of Life Sciences at the University of Lincoln in the U.K., examined 19 embryos and 37 eggs from Hamipterus tianshanensis, which had been found in Argentina and China. Some embryos were in middle to late stages of development, while others were fully developed, the study authors reported.

To determine embryonic stages and calculate the pterosaurs' potential wing power, the researchers looked at ossification in the embryos' skeletons; this process shapes the skeletons as the embryos grow. They found that late-stage and near-term embryos had all the skeletal elements required for flight, while hatchlings showed fossilized evidence of wing membranes "with a complex internal structure related to how the membrane is used in flight," Unwin said in the email.

The scientists also discovered that the shapes of the eggs could hold clues about developmental stages. Pterosaurs laid leathery, soft-shelled eggs, like those of modern reptiles. Lizard and snake eggs are known to change their shapes as they absorb water to nourish the embryo over time, increasing the egg's mass, length and width.

According to the study, pterosaur eggs did the same; the shape and size of the eggs could therefore reveal how close they were to hatching. [See Photos of the Remains of Baby Pterosaurs]

"It matches what we know of soft-shelled eggs in living animals," said Michael Habib, an assistant professor of clinical integrative anatomical sciences with the Keck Institute of Medicine at the University of Southern California. Habib, who studies pterosaurs, wasn't involved in the new study.

Powering up

However, questions remain about whether skeletal ossification in the embryos' limbs is a reliable indicator of flight ability, said Armita Manafzadeh, a doctoral candidate in the Department of Ecology and Evolutionary Biology at Brown University in Rhode Island.

"Living birds (and bats) whose limb bones are well-ossified in late embryonic and early post-hatching stages still cannot yet fly — largely invalidating a key premise of the authors' argument," Manafzadeh told Live Science in an email.

According to Manafzadeh, who also wasn't part of this new study, recent research has shown that birds capable of early flight have bones that are well-ossified before and after hatching — yet flight muscles and joint surfaces in these birds' forelimbs change dramatically after they hatch, suggesting that ossification alone is not enough to power their flight.

"It's only after these additional musculoskeletal changes take place that juvenile birds are capable of generating the aerodynamic forces necessary for flight, which is the most power-demanding mode of locomotion, Manafzadeh said.

If flaplings were able to fly after hatching, that could mean that they were able to feed and take care of themselves, negating the need for extensive parental care, the researchers wrote in the study. In that scenario, baby pterosaurs would be active participants in their ecosystems and not helpless hatchlings wholly dependent on their parents. This new perspective has implications for scientists working to reconstruct the environments where pterosaurs lived, Habib said.

If the flaplings could fly right out of the gate, that brings up another challenge: How could they grow and fly at the same time? And how would they weather the metabolic and mechanical demands of flight on their small bodies, Habib asked.

"While our findings help solve one problem, they have also opened up many more interesting questions," Unwin said. "We are only at the beginning of understanding these extraordinary creatures."

The findings were published online June 12 in the journal Proceedings of the Royal Society B.

• Photos: Ancient Pterosaur Eggs & Fossils Uncovered in China
• In Images: A Butterfly-Headed Winged Reptile
• In Photos: Bizarre 'Bat Dinosaur' Discovered in China

Originally published on Live Science.

Paleontologists have discovered the remains of an ancient Loch Ness Monster look-alike in freezing Antarctica. And just like the legendary Nessie, it wasn't the runt of the litter.

The prehistoric plesiosaur — a four-flippered marine reptile that lived during the dinosaur age — measured a colossal 36 feet (11 meters) long from snout to tail, about as long as a modern telephone pole. This newfound "sea monster" is now the largest known elasmosaurid (a type of plesiosaur with a long neck) on record.

"Not only is it quite long, it's also quite stocky" and weighed nearly 15 tons (13.4 metric tons) when it was alive, making it the heaviest known elasmosaurid, said study lead researcher José O'Gorman, a vertebrate paleontologist at the La Plata Museum and the National University of La Plata in Argentina. [Photos: Uncovering One of the Largest Plesiosaurs on Record] 

Researchers discovered the fossils of the enormous plesiosaur on Antarctia's Seymour Island (known as "Marambio" in Argentina) in 1989. But the beast was so large and the rock was so hard that it took three return trips — in 2005, 2012 and 2017 — to fully extricate the specimen. During that time, the scientists collected 1,760 lbs. (800 kilograms) of fossilized bones embedded in rock.

On the island, the fossils lay hidden in the López de Bertodano Formation, just 7.5 feet (2.3 meters) below the K/Pg boundary, the geologic line showing the Cretaceous–Paleogene extinction. This notorious extinction led to the demise of the nonavian dinosaurs and plesiosaurs, when a 6-mile-long (10 kilometers) asteroid collided with Earth about 66 million years ago.

Given the fossils' proximity to the K/Pg boundary, this ancient sea monster likely lived 30,000 years before that mass extinction, O'Gorman told Live Science.

This particular plesiosaur likely falls within the genus Aristonectes, but the scientists aren't sure if it's a new species, said O'Gorman, who is also part of National Scientific and Technical Research Council of Argentina (CONICET). That's because the newfound fossils don't overlap enough with those of other specimens, making comparisons difficult, he said.

In other words, the nickname Nessie might be most appropriate, given the creature's striking resemblance.

That said, Aristonectes' remains do shed light on its life. Parts of its vertebrae were fused together, indicating that the creature was a fully grown adult, the researchers found. And although this Aristonectes was a huge beast, its neck wasn't as elongated as those of other elasmosaurids, because it literally had fewer neck vertebrae. That's why researchers call it "stocky," O'Gorman noted.

Even its location fits in with the track record of its relatives, as other late Cretaceous elasmosaurid fossils have been found in the southern portion of the world, including Patagonia (a region in southern Argentina and Chile), western Antarctica and New Zealand, the researchers said.

This newfound Aristonectes likely dined on invertebrates, that is, animals without backbones, such as jellyfish. This specimen's huge size indicates that its ecosystem was flourishing and likely replete with tasty prey, O'Gorman said. Such plentiful conditions may have lasted until the mass extinction, he added.

The study, which was largely funded by Argentina's National Antarctic Directorate and the Argentine Antarctic Institute, will be published in the October issue of the journal Cretaceous Research.

• Image Gallery: Ancient Monsters of the Sea
• Image Gallery: 25 Amazing Ancient Beasts
• 15 of the Largest Animals of Their Kind on Earth

Originally published on Live Science.

This small but fierce "mini rex" was a lightweight compared with the dinosaur king. Now dubbed Suskityrannus hazelae, the tyrannosaur would have tipped the scales at no more than 90 lbs. (40 kilograms). In contrast. T. rex weighed a whopping 18,000 lbs. (8,160 kg).

"The animal would have looked a bit more like the "Jurassic Park" Velociraptors in terms of size and head height than its later huge relatives, like T. rex," said study lead researcher Sterling Nesbitt, an assistant professor in the Department of Geosciences at the Virginia Tech College of Science. [Photos: Tiny Tyrannosaur Dinosaur Was About As Big As T. Rex's Skull]

Nesbitt found the remains of this incredible dinosaur when he was a pipsqueak himself — just a 16-year-old high-school student who was on a dig expedition in western New Mexico in May 1998. That dig was led by Doug Wolfe, the co-founder and CEO of the Zuni Dinosaur Institute for Geosciences in Springerville, Arizona, who is a co-author on the study.

In fact, the first partial skull of the mini tyrannosaur was found in 1997 by Robert Denton, now a senior geologist with Terracon Consultants, an engineering consulting firm in New Jersey. As a teenager, Nesbitt was keen to find more of that specimen, so he went to the same location to hunt for related bones. But "on my way there, I found the remains of the more complete specimen," Nesbitt told Live Science in an email. "I spent the next few days with my eyes glued to the ground looking for all the little fragments of bone."

The specimen Nesbitt found is so complete, it's helping researchers learn about this wee tyrannosaur, which predates T. rex by about 25 million years.

For instance, S. hazelae stood about 3 feet (1 m) tall at the hip and measured about 9 feet (3 m) from head to tail. To put that in perspective, the skull of Sue the T. rex at the Field Museum in Chicago is about 5 feet (1.5 m) long.

In addition, the unique anatomy of S. hazelae shows how the older and smaller tyrannosauroids from North America and China were linked to the larger tyrannosaurids that lasted until the asteroid slammed into Earth about 66 million years ago. In fact, S. hazelae is one of the last small tyrannosauroids on record. The lineage of T. rex and S. hazelae date back to the middle Jurassic, but it wasn't until the end of the Cretaceous period, about 85 million years ago, that these dinosaurs got huge, Nesbitt said.

"Suskityrannus is a key link between the enormous bone-crunching dinosaurs like T. rex and the smaller species they evolved from," Steve Brusatte, a paleontologist at the University of Edinburgh, who was not involved in the study, said in a statement. "The new species shows that tyrannosaurs developed many of their signature features like a muscular skull, broad mouth and a shock-absorbing foot when they were still small, maybe as adaptations for living in the shadows."

Unfortunately, the Cretaceous-age tyrannosaur died as a youngster; S. hazelae was only about 3 years old when it expired, according a growth ring analysis of its bones. (Like trees, dinosaur bones laid down new rings as the animal grew.)

The study was published online today (May 6) in the journal Nature Ecology & Evolution.

• Photos: Newfound Tyrannosaur Had Nearly 3-Inch-Long Teeth
• Baby T. Rex Was an Adorable Ball of Fluff
• In Images: A New Look at T. Rex and Its Relatives

Originally published on Live Science.

Tiny predator

An artist's interpretation of the tiny tyrannosaur, dubbed Suskityrannus hazelae. In the background are a small horned dinosaur known as Zuniceratops and the hadrosauromorph Jeyawati.

[Read more about the tiny tyrannosaur]

Bone display

The fossilized bones of S. hazelae, which lived about 92 million years ago in what is now western New Mexico.

High school discovery

Study lead researcher Sterling Nesbitt, an assistant professor of geosciences at Virginia Tech, holds the partial skull of S. hazelae. Nesbitt found this particular specimen while he was a 16-year-old high school student in 1998.

Big jaw, little jaw

S. hazelae was small compared to its giant relative, Tyrannosaurus rex. Notice how small the partial skull of S. hazelae is (top) compared with a cast of a full-size partial jaw of T. rex (bottom).

Future paleontologist

Nesbitt found the fossils of S. hazelae when he was a teenager. The 1998 dig was led by Doug Wolfe, of the Zuni Dinosaur Institute for Geosciences in Springerville, Arizona, who is also an author on the new study.

The claw

The fossilized claw of S. hazelae.

Tiny beast

The dinosaur stood about 3 feet (1 meter) tall at the hip and measured about 9 feet (3 m) long from snout to tail. The S. hazelae discovery is helping researchers understand how tyrannosaurs started small and then became huge over millions of years of evolution.

Skeletal reconstruction

A skeletal reconstruction of S. hazelae. Researchers have discovered two individuals of this tiny (at least by T. rex standards) dinosaur. Nesbitt found one and Robert Denton, now a senior geologist with Terracon Consultants, an engineering consulting firm in New Jersey, found a partial skull of another individual in 1997.

About 99 million years ago, a Cretaceous millipede scampered over the forest floor in what is now Southeast Asia. The arthropod successfully avoided being squished by neighboring dinosaurs, but it had the bad fortune to stumble into a sticky patch of sap, which hardened around the millipede and locked it into an amber tomb.

While that was a terrible outcome for the millipede, it was great news for the scientists who recently discovered the tiny corpse.

The entombed fossil, of a female measuring 0.3 inches (8.2 millimeters) in length, was so well-preserved that its minuscule body structures were retained in exceptional condition. This enabled scientists to identify the tiny arthropod as not only a previously unknown species, but a previously unknown suborder as well, adding a branch to the millipede family tree. [Fabulous Fossils: Photos of the Earliest Animal Organs]

Using micro-computed X-ray tomography (micro-CT) scans, the scientists constructed a digital 3D model of the millipede, which was curled into an "S" shape inside the lump of amber. The creature had 35 body rings and fully developed sperm-storing sacs on its underside, which confirmed that the female specimen was a mature adult, the study authors said.

Today, millipedes are abundant and diverse, with about 11,000 species identified and as many as 80,000 species estimated to exist worldwide, the researchers said in a new study. But little is known about fossil millipedes, and there are only a handful of experts worldwide investigating this group, said lead study author Pavel Stoev, a professor of zoology at the National Museum of Natural History, Sofia in Bulgaria.

Evidence in the fossil record shows that millipedes were around as early as 315 million to 299 million years ago, with some growing to nearly 8 feet (2 meters) in length, Stoev told Live Science in an email.

"Prior to our study, there were only four species of millipedes described from Burmese amber, which is known to be among the oldest and richest amber deposits of Cretaceous fauna," Stoev said.

Other than the millipede's unusually small size, several clues told the scientists that this specimen differed from the three other suborders within the Callipodida order. It lacked certain hair-like growths; the shape of its rear segment was unique, and while most callipodidans' compound eyes contain at least 30 optical units, the little millipede's eyes held only five — "the lowest limit known in the group," Stoev said.

The researchers named a new suborder, Burmanopetalidea, and dubbed the arthropod Burmanopetalum inexpectatum. The first part of that name references where the amber came from — Burma, now Myanmar — while "inexpectatum" is Latin for "unexpected," celebrating the surprise discovery of a new millipede suborder, according to the study.

The findings were published online today (May 2) in the journal Zookeys.

• Photos: Ancient Ants & Termites Locked in Amber
• Amber Trap Nabs Feathered Dino Tail (Photos)
• Hatchling Preserved in Amber (Photos)

Originally published on Live Science.

An ancient crab that lived during the dinosaur age was so strange, paleontologists are calling it the platypus of the crab world.

This newly discovered critter — named Callichimaera perplexa, which means "perplexing beautiful chimera" — had a hodgepodge of body parts. That name references the mythical chimera from Greek mythology, which had a lion's head, a goat's body and a snake's tail.

But unlike the mythological version, this bizarre chimera actually existed: It had the mouth of a shrimp, the claws of a modern frog crab, the shell of a lobster and the paddle-like appendages of a sea scorpion, the researchers found. Its eyes were so giant that it would be like a human with soccer ball-size peepers, said study lead researcher Javier Luque, a postdoctoral fellow in paleontology at Yale University and the University of Alberta in Canada. [Photos: Ancient Crab is the Strangest You've Ever Seen]

"[It had] huge, enormous eyes," Luque told Live Science. "They're like Little Red Riding Hood [when she asks the wolf], 'What big eyes you have. What do you use them for?'"

In this case, C. perplexa likely used its large eyes, not to mention its powerful claws, to hunt tiny crustaceans, such as comma shrimp. "We don't think they were filter feeders," Luque said. "We think they were actually active predators."

Unexpected discovery

Luque made the first discovery of C. perplexa remains in 2005 while hunting for fossils as an undergraduate student in Pesca, a town high in the Colombian Andes Mountains. "They were leggy-looking things," he said. "It looked like a crab, but I thought it was more like a spider."

After much study, he found that the critter was a weird, quarter-size crab that lived about 95 million to 90 million years ago, during the Cretaceous period. Within a few years, he heard tales of similar fossil crabs discovered in Wyoming and Morocco. Soon, he had more than 70 specimens of this tiny crustacean, including babies, adults, males and females.

Given that these crabs were found in such different places and environments, they were likely highly adaptable, Luque said. C. perplexa is so extraordinary, it forms an entirely new branch of the evolutionary tree for crabs, he added.

In addition to looking like a mix of different animals, this swimming crab also looked like a combination of baby and adult parts. For instance, grown individuals had large, socketless compound eyes; bent claws; leg-like mouth parts; an exposed tail; and a long body — all of which are seen in crab larvae.

In essence, the discovery of C. perplexa shows that "true crabs" lost and reevolved their body plans many times throughout history, Luque said.

"I call it my beautiful nightmare because it was so beautiful and frustrating" to figure out, Luque said.

The study was published online today (April 24) in the journal Science Advances.

• See 15 Crazy Animal Eyes — Rectangular Pupils to Wild Colors
• Image Gallery: Tiny Crustaceans Found in Fossil Reef
• Photos: Unique Life Found at East Coast Gas Seep

Originally published on Live Science.

Giant eyes

Here is an illustration of Callichimaera perplexa, quite possibly the strangest looking crab that ever lived.

[Read more about the strange crab]

Crabby fossil

Yale paleontologist Javier Luque found C. perplexa in Colombia in 2005. Since then, C. perplexa specimens have also turned up in Wyoming and Morocco.

Tiny crab

C. perplexa lived during the last dinosaur age, the Cretaceous period, about 95 million years ago.

Crustacean diversity

Crabs come in many shapes and sizes. But C. perplexa (center) might be the strangest of all of them. It has giant baby-like eyes, a lobster-like shell, the claws of a frog crab and paddles like an ancient sea scorpion.

Excavation

Paleontologist Javier Luque searches for fossil crabs in the Colombian Andes.

Amazing find

This extinct crab is a chimera, meaning it combines traits from several extinct and living crabs and crustaceans.

Digging away

Luque (left) and Catalina Suarez, with the Colombian Geological Survey (center) dig for fossils in the Colombian Andes.

[Read more about the strange crab]

The partial skeleton of a baby Tyrannosaurus rex is for sale on eBay for nearly $3 million. And while it's anyone's guess who (if anyone) will buy the "king of the dinosaurs," the seller is certain of one thing: The specimen will inevitably end up in a museum, he said.

"I'll guarantee you it will" eventually land in a museum, Alan Detrich, a sculpturist and professional fossil hunter in Kansas who is auctioning the T. rex, told Live Science. According to Detrich, if some billionaire purchases the specimen, he or she will likely — for tax purposes — gift the dinosaur to a museum one day.

In that case, "everybody is happy because the [T. rex] is in a museum, and the billionaire got patted on the back and rode off into the sunset on the back of a dinosaur," Detrich said. [In Images: A New Look at T. Rex and Its Relatives] 

Detrich listed the baby T. rex on eBay on Feb. 26, and the paleontological community has been in an uproar ever since. Legality has nothing to do with the anger. Detrich's brother Bob found the beast's fossilized bones near Jordan, a town in eastern Montana, in 2013. Detrich was leasing the land, which was private property, meaning anything found on the land belonged to Detrich.

Rather, paleontologists are upset because if a private individual buys the baby dinosaur king, that person is under no obligation to share it with the scientists who are keen to study juvenile T. rex specimens. Moreover, even if the predator's remains were lent to an institution or made available for study, most paleontologists don't like to study fossils unless they're donated, meaning the specimen would be available for study in perpetuity, and not just when the owner feels like making it accessible.

That's precisely what happened in 2016, when a privately owned, 120-million-year-old specimen from Brazil drew controversy: A group of scientists called it the first four-legged snake on record, and another group announced that it wasn't a snake at all, but likely a dolichosaurid, an extinct snake-like marine lizard. It's anyone's guess what the creature really is, as the specimen's owner has declined to let anyone else study the fossil.

Finding Baby Bob

After digging up the bones, Detrich immediately knew they belonged to a theropod (a group of bipedal, mostly meat-eating dinosaurs), but he didn't know it was a T. rex until he took it to Peter Larson, a paleontologist and president of the Black Hills Institute of Geological Research in South Dakota.

Excited, Detrich took the fossils home to Kansas and cleaned them up. Then, in honor of his late mentor, Larry Martin, a vertebrate paleontologist and curator of the Natural History Museum at the University of Kansas, he lent it to the museum.

"In honor of Larry, I thought it would be a good thing if I loaned this thing to the museum," Detrich said. "They could study it, they could show thousands of people this specimen, and they have." Paleontologists contacted by Detrich looked at the bones and estimated that the dinosaur, initially named "Baby Bob" and later "Son of Samson," was about 4 years old when it died during the late Cretaceous, about 68 million years ago. [Gory Guts: Photos of a T. Rex Autopsy]

But after Son of Samson was on display for two years, Detrich felt like "I did my fair share of giving," and he posted it on eBay for $2.95 million. He didn't initially tell the museum about his plans, but when museum officials found out, they asked that he remove their name from the eBay posting, so they wouldn't be associated with the auctioning of dinosaur fossils.

In a statement, museum director Leonard Krishtalka said, "The KU Natural History Museum does not sell or mediate the sale of specimens to private individuals. Accordingly, the specimen on exhibit-loan to us has been removed from exhibit and is being returned to the owner. We have asked that the owner remove any association with us from his sale listing."

The Society of Vertebrate Paleontology also decried the sale: "Vertebrate fossils are rare and often unique," the society said in a statement. "Scientific practice demands that conclusions drawn from the fossils should be verifiable: scientists must be able to reexamine, remeasure and reinterpret them (such reexamination can happen decades or even centuries after the fact)."

What's the big deal?

Studying privately owned specimens is so discouraged that Robert Boessenecker, a postdoctoral researcher in the Department of Geology and Environmental Geosciences at the College of Charleston in South Carolina, who isn't involved with the T. rex specimen, said he wouldn't study any, even if the owner offered to lent it to him or a museum.

In fact, it's common for people to try to drop off privately owned specimens for Boessenecker to identify, shed light on or even put on temporary display.

"That has already happened, and I have thanked them for their generosity, but explained that because museums serve as a center of research, that any fossil that enters the museum for a long-term period should be owned by the museum," Boessenecker said. "If we're going to put it on display, it has to be a fossil that has been donated or otherwise permanently accessioned [added] into our collection."

He added that most museums don't have the budget to purchase high-priced specimens. (An exception is Sue, the most complete T. rex on record, who was sold to the Field Museum of Natural History in Chicago for $8.4 million in 1997.) Instead, most research institutions opt to spend less money by sending their own researchers out into the field to find fossils, or rely on the generosity of donors, Boessenecker said. [Photos: Velociraptor Cousin Had Short Arms and Feathery Plumage]

Boessenecker added that many paleontologists have good relationships with fossil collectors, who often clue in researchers to fossil hotspots and exciting finds. But if they want to loan a specimen, it's just not worth it, Boessenecker said, in part because the museum is responsible for the housing and safety of any fossils in its possession. (He detailed other challenges in this Twitter thread.)

Moreover, Detrich's eBay listing hints that the juvenile T. rex might solve the Nanotyrannus mystery once and for all. In short, some experts think that Nanotyrannus is a separate species, but most paleontologists think it's simply a baby T. rex. However, while the teeth of such a specimen would shed light on the mystery one way or the other, Boessenecker noted that Son of Sampson's jaw is highly fragmented and part of it may be missing — so it likely wouldn't solve the case.

In the meantime, the Society of Vertebrate Paleontology discouraged institutions from putting loaned items on display.

"We strongly recommend that repositories, exhibitions and scientists stay at arm's length from specimens that are not yet permanently in the public trust," the society said in the statement. To give an example, "The Museum für Naturkunde [Natural History Museum] in Berlin is currently exhibiting and studying a privately owned tyrannosaur skull, a specimen that could just as easily be removed from the public trust as Detrich's juvenile," the society said.

While there are no bids on the T. rex yet, as Detrich told Live Science, "All you need is one."

• Photos: See the Armored Dinosaur Named for Zuul from 'Ghostbusters'
• Photos: Newfound Dinosaur Had Tiny Arms, Just Like T. Rex
• Photos: The Near-Complete Wankel T. Rex

Originally published on Live Science.

Exquisite preservation

At a site in North Dakota, researchers have discovered a multitude of fossils of animals that died together about 66 million years ago. They were likely buried by an enormous wave of mud, generated by the asteroid impact that marked the end of the reign of the dinosaurs.

Read more about the Cretaceous "death pit"

Shaped by the impact

The site, called "Tanis" by the scientists, was seeded with tiny beads called spherules, formed from droplets of molten rock that were hurled into the atmosphere after the asteroid struck. They rained down into Tanis shortly before the site was buried under a wave of mud.

Glass at the center

At Tanis, spherules, also called tektites, were covered with clay but had a glass core.

Caught in the gills

Study co-authors Robert DePalma and Jan Smit photograph freshly exposed impact spherules in fish gills at Tanis.

Rock layers

A cross-section of the Tanis deposit shows some animal fossils and layered stratigraphy from two surge pulses.

Mass death

Animals that were preserved at Tanis died at the same time "on the last day of the Cretaceous," lead study author Robert DePalma told Live Science.

Swept away

Multiple fish carcasses (R) and tree logs were tossed together by a massive inundation surge, forming part of the mass-death layer at Tanis.

Peering at the past

Study co-author David Burnham examines a specimen collected at Tanis.

Preserved fish

Fish that fossilized after they were buried 66 million years ago maintained a 3D shape, after their bodies filled with mud.

Asphyxiated then buried

Spherules were caught in the gills of about 50 percent of the freshwater fish that the researchers examined at Tanis. The fish likely aspirated the spherules that rained down on the river valley after the faraway asteroid impact, prior to the giant wave of mud that buried them.

Marine mollusk fossil

A small fragment of fossilized shell at Tanis belonged to an ammonite — an extinct group of marine mollusks related to modern octopus, cuttlefish and squid. This and other marine fossils were swept into the river valley by an enormous wave from the sea nearby.

Amber in UV

At Tanis, spherules were preserved in tiny blobs of amber clinging to buried branches and logs. The amber is hard to see in visible light (left) but glows bright green under ultraviolet (UV) light.

"Rain" of spherules

Scanning electron microscope (SEM) images reveal surface details in microkrystites — microscopic spheres that peppered Tanis, formed from molten rock ejecta at the site of the asteroid impact near Chicxulub, Mexico.

Protected with plaster

Field excavations at Tanis in North Dakota, part of the fossil-rich Hell Creek Formation that spans North Dakota, South Dakota, Wyoming and Montana.

Dividing line

Study co-authors Peter Larson and Robert DePalma, and field assistant Lindsay Powell investigate a geological layer separating the Cretaceous and the Tertiary periods. Known as the KT boundary, this layer contains material that settled across the planet after the asteroid impact 66 million years ago.

Under the microscope

Study co-author Lauren Gurche holds a microscope slide of ejecta spherules from Tanis.

The New Yorker recently described a so-called dinosaur graveyard as holding the remains of an astonishingly diverse trove of dinosaur fossils, including hatchlings; it caused quite a buzz in the media. But even though the site is potentially groundbreaking, the New Yorker article is out of step with the study describing the find.

There's no question that the site in North Dakota (part of the fossil-rich Hell Creek Formation) is an incredible paleontology bonanza; crammed with Cretaceous fossils that were all buried at once, it offers an unprecedented snapshot of the minutes and hours following the asteroid impact that extinguished much of life on Earth around 66 million years ago.

On March 29, prior to the study's publication in a scientific journal, The New Yorker reported that the site contained fossils of pterosaurs, mammals and "almost every dinosaur group known from Hell Creek." However, the study — published online Monday (April 1) in the journal Proceedings of the National Academy of Sciences — makes no mention of dinosaurs, apart from an isolated and incomplete hip bone. [Crash! 10 Biggest Impact Craters on Earth]

"There seems to be a disconnect between what is described in The New Yorker with what is actually in the peer­-reviewed paper," Stephen Brusatte, a reader in vertebrate paleontology at the School of Geosciences at the University of Edinburgh in the United Kingdom, told Live Science in an email.

Brusatte, who was not involved in the new study, said that the claim would be "awesome" if it were true, but for now, the data simply isn't available.

"I hope there are other dinosaur fossils at the site, and I look forward to hearing more about them," he said.

Lead study author Robert DePalma, who conducted the research as a doctoral candidate in geology at the University of Kansas (KU), told Live Science that "the only information that anyone should be talking about is what's in this published paper, because that's the only thing that can be freely evaluated based on the scientific data."

Densely packed fossils

The Cretaceous period (145.5 million years ago to about 65.5 million years) literally ended with a bang. Scientists cite a massive asteroid impact in waters near Chicxulub, Mexico, as the prevailing explanation for the sudden disappearance of most of Earth's animal species — including all dinosaurs except birds.

When the asteroid struck, it ended the Cretaceous and ushered in the Paleogene. The newly described site lies between layers of Cretaceous and Paleogene rocks at the Hell Creek Formation, one of the world's richest fossil deposits, which spans parts of Montana, North Dakota and South Dakota. The site contains densely packed fossils of animals that died at the same time "on the last day of the Cretaceous," said DePalma, who is currently a researcher at the KU Biodiversity Institute and Natural History Museum, and an adjunct professor at Florida Atlantic University.

"Their presence there, and the presence of all the other details in sediments, is helping us to tease out all the little, tiny details that occurred in the first moments after the impact that were unclear before this discovery," DePalma said.

DePalma dubbed the site "Tanis" after the city that hid the ark of the covenant in the film "Raiders of the Lost Ark," according to The New Yorker. The fossil deposit appears to contain something equally as remarkable and unprecedented as its namesake: evidence of mass death directly linked to the Chicxulub impact.

Fish and ammonites

In the study, DePalma and his colleagues described a deposit about 3 feet (1.3 meters) thick, holding fossil evidence of freshwater fish, marine vertebrates, ammonites (extinct relatives of today's nautilus), vegetation and animal-made burrows.

More than 50 percent of the freshwater fish at Tanis died with tiny glass balls called spherules embedded in their gills; in fact, the site was riddled with spherules ranging in diameter from 0.01 to 0.06 inches (0.3 to 1.4 millimeters).

Also known as tektites, these glass beads formed from droplets of melted rock that were sprayed into the atmosphere after the asteroid's impact. These objects rained down on North America minutes later, and the Tanis fish probably inhaled and choked on the tektites before a wave of debris buried the creatures, the researchers reported.

Researchers also found spherules embedded in amber adhering to bits of branches and tree trunks; the amber coating prevented these tektites from deforming and preserved their original shapes. The glass beads are "geochemically nearly indistinguishable" from glass found at the Chicxulub site, and thereby "directly correlate with the Chicxulub impact," the scientists wrote in the study.

In the marine area around the Chicxulub impact, spherules are commonly found "many layers below the mass extinction and many layers above it," Gerta Keller, a professor of geosciences at Princeton University, told Live Science. Kelly, who was not involved in the study, explained that storms or a drop in sea level can shift spherules into younger geologic deposits, so that they appear to have originated there — even if they are older than the rocks around them.

But at Tanis, spherules were stuck in amber and in the gills of dead fish, suggesting that spherules and fish were all buried at the same time, the study said. [Wipe Out: History's Most Mysterious Mass Extinctions]

A deadly surge

After the rain of tektites, the water came. Clues in Tanis' sediments and in the positions of the buried fossils hinted that an enormous wave more than 34 feet high (11 m) surged into the river valley from the nearby sea. Sand and mud carried by the wave swiftly buried animals and plants at Tanis, DePalma said.

The surge swiftly traveled inland, flowing from west to east — the opposite direction of the ancient river's flow — so the scientists quickly ruled out typical river flooding as the cause of mass death, DePalma said. Only a tsunami or a seiche, a towering wave that forms in large bodies of water, could create the deposit that the scientists found. It was likely caused by the seismic waves generated by the Chicxulub asteroid, the researchers reported.

Dozens of sites around the globe exhibit a geologic layer marking the end of the Cretaceous. That layer, rich in spherules and minerals that drifted to Earth after the asteroid impact, draws a stark division between global diversity as the Cretaceous was winding down and the dramatic disappearance of numerous plant and animal species that followed, Kirk Johnson, director of the Smithsonian Museum of Natural History in Washington, D.C., told Live Science.

What makes the Tanis site exceptional is that it preserves a moment in time "during the catastrophe itself," as the disaster unfolded 66 million years ago, said Johnson, who was not involved in the study.

"That's the incredible thing about this — it gives you some texture on what was happening on that day when the asteroid hit," Johnson said.

Tanis has only begun to yield its long-buried secrets — to the study authors and other research teams, DePalma said. The mass extinction that followed the Chicxulub impact wasn't the first in Earth's history, and it likely won't be the last; nevertheless, the Tanis site offers a rare perspective on what can happen during a global extinction event, which could inform how we cope with similar challenges to come, DePalma said.

"If we can understand how the world responds to things like that, we can understand how we might begin to deal with an extinction-level event today," he said.

• Meteor Crater: Experience an Ancient Impact
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Editor's Note: The article was updated to reflect Robert DePalma's affiliation at the time that the research was conducted.

Originally published on Live Science.

The mightiest Tyrannosaurus rex on record is a behemoth named Scotty, who — during its lifetime on Earth about 65 million years ago — weighed a honking 19,555 lbs. (8,870 kilograms), or about as much as 6.5 Volkswagen Beetles, a new study finds.

Scotty was so massive, it edged out Sue, the famous T. rex at the Field Museum of Natural History in Chicago, as heavyweight champ.

In all, Scotty is about 880 lbs. (400 kg) heavier than Sue, "which is a lot by human standards, but not as much when you're dealing with a tyrannosaur," said study lead researcher Scott Persons, a paleontologist at the University of Alberta. [Gory Guts: Photos of a T. Rex Autopsy] 

Researchers originally found Scotty in 1991, near the town of Eastend, Saskatchewan. But it took years to dig out and then prepare the dinosaur king, because the rock the fossils were embedded in was so "gosh darn hard," Persons told Live Science. That rock — heavily cemented sandstone rich in iron — was part of the Frenchman Formation, which dates to the late Cretaceous period, from about 72 million to 65 million years ago.

T. rexes, however, lived for only the last 2 million years of the Cretaceous, or from about 67 million to 65 million years ago.

The researchers were so thrilled at the find, they celebrated it with a toast. "The only spirit that was on hand was on old bottle of scotch," Persons said, which inspired them to name the T. rex Scotty. However, it's unclear whether Scotty was male or female, Persons noted.

After all of Scotty's fossils were prepared, researchers found they had about 65 percent of the skeleton, including the skull, the braincase (the part of the skull that holds the brain); the lower jaw; vertebrae from the neck, back and tail; and parts of the hips, leg and shoulder.

However, Scotty isn't the heaviest dinosaur on record. That honor likely goes to the long-necked Argentinosaurus, who could have weighed up to 110 tons (100 metric tons), according to some estimates. (The feat of determining dinosaur mass is a highly debated subject, as there are different ways to calculate it. In this case, scientists determined Scotty's mass by comparing the proportion of its bones and plugging these measurements into a formula, Persons said.)

Moreover, while Scotty is the heaviest T. rex on record, it's not the longest. A T. rex named Stan, who is on display at the Black Hills Institute of Geological Research, spans nearly 40 feet (12.2 m) from snout to tail. In addition, the most complete known T. rex remains Sue, who is about 90 percent complete.

But Scotty has other claims to fame. For instance, it likely reached its 30th birthday, making it the longest-lived T. rex on record, according to a bone analysis by study co-researcher Gregory Erickson, a professor of anatomy and vertebrate paleobiology at Florida State University. Erickson did this by looking at the growth rings in the dinosaur's bones (like trees, dinosaur bones laid down new rings as they aged.)

Scotty's bones also preserved the dinosaur's dramatic injuries, all of which had healed by the time the dinosaur died. These included a broken jaw, broken ribs and a pressed series of vertebrae that Scotty sustained during its "violent and unusually long life," the researchers wrote in the study.

They added that the "relative scarcity of other equally large and mature T. rex specimens" suggests that these beasts tended to die before they passed the 8.8-ton (8 metric tons) threshold.

Scotty will be on public display at the Royal Saskatchewan Museum in Regina, Saskatchewan, this May. The study was published online March 21 in the journal The Anatomical Record.

• Photos: The Near-Complete Wankel T. Rex
• Photos: Newfound Dinosaur Had Tiny Arms, Just Like T. Rex
• Baby T. Rex Was an Adorable Ball of Fluff

Originally published on Live Science.