T. Rex not as smart as previously claimed

Dinosaurs were as smart as reptiles but not as intelligent as monkeys, as former research suggests.

An international team of palaeontologists, behavioural scientists and neurologists have re-examined brain size and structure in dinosaurs and concluded they behaved more like crocodiles and lizards.

In a study published last year, it was claimed that dinosaurs like T. rex had an exceptionally high number of neurons and were substantially more intelligent than assumed. It was claimed that these high neuron counts could directly inform on intelligence, metabolism and life history, and that T. rex was rather monkey-like in some of its habits. Cultural transmission of knowledge as well as tool use were cited as examples of cognitive traits that it might have possessed.

However the new study, published today in The Anatomical Record, involving the University of Bristol's Hady George, Dr Darren Naish (University of Southampton) and led by Dr Kai Caspar (Heinrich Heine University) with Dr Cristian Gutierrez-Ibanez (University of Alberta) and Dr Grant Hurlburt (Royal Ontario Museum) takes a closer look at techniques used to predict both brain size and neuron numbers in dinosaur brains. The team found that previous assumptions about brain size in dinosaurs, and the number of neurons their brains contained, were unreliable.

The research follows decades of analysis in which palaeontologists and biologists have examined dinosaur brain size and anatomy, and used these data to infer behaviour and lifestyle. Information on dinosaur brains comes from mineral infillings of the brain cavity, termed endocasts, as well as the shapes of the cavities themselves.

The team found that their brain size had been overestimated -- especially that of the forebrain -- and thus neuron counts as well. In addition, they show that neuron count estimates are not a reliable guide to intelligence.

To reliably reconstruct the biology of long-extinct species, the team argues, researchers should look at multiple lines of evidence, including skeletal anatomy, bone histology, the behaviour of living relatives, and trace fossils. "Determining the intelligence of dinosaurs and other extinct animals is best done using many lines of evidence ranging from gross anatomy to fossil footprints instead of relying on neuron number estimates alone," explained Hady from Bristol's School of Earth Sciences.

Dr Kai Caspar explained: "We argue that it's not good practice to predict intelligence in extinct species when neuron counts reconstructed from endocasts are all we have to go on."

"Neuron counts are not good predictors of cognitive performance, and using them to predict intelligence in long-extinct species can lead to highly misleading interpretations," added Dr Ornella Bertrand (Institut Català de Paleontologia Miquel Crusafont).

Read more at Science Daily

8 in 10 lizards could be at risk due to deforestation

In Colorado, people flock to the Rocky Mountains when the summer heat gets unbearable. Animals seek shelter too when temperatures become extreme, and forests serve as critical sanctuaries for small tree-dwelling animals like lizards.

In a new study published March 5 in the journal Nature Climate Change, scientists from the University of Colorado Boulder and Tel Aviv University in Israel revealed that deforestation combined with climate change could negatively impact 84% of North America's lizards by the end of the century. Nearly one in five could face population decline.

Unlike mammals that can maintain their body temperatures in a variety of ways -- sweating when it gets too hot and relying on warm fur when it gets too cold -- cold-blooded animals like lizards have limited strategies to thermoregulate. Tree-climbing lizards move around tree trunks to bask in the sun for warmth. When the ground gets too hot, they climb higher or move into the shade.

"What's really interesting about lizards is that they just need to be able to move a short distance around the tree trunk to get to a very different climate and habitat environment," said Keith Musselman, an assistant professor in the Department of Geography and CU Boulder's Institute of Arctic and Alpine Research. "These microhabitats are particularly important when we think about how we modify our natural environment and make conservation decisions."

Using computer simulations, the team showed that global warming can actually benefit lizards living in colder regions or at higher latitudes in North America. Warmer weather increases the animals' activity time, meaning they have more time to look for food or mates during the day. However, deforestation would largely reverse these positive effects by reducing opportunities for shade in hotter climates that help them cool down.

The team simulated lizard models for different climate regions across North America. They found that tree loss could decrease lizards' activity time by an average of 34% by the end of the century. Without trees, the animals would have to hide under rocks or in caves to avoid overheating. The impact would be especially prominent for species that already live in warmer regions, where future summers will become too warm for activity on the ground.

The team estimated that deforestation would accelerate population declines for 18% of lizards in North America.

"Our work provides new insights into the mechanisms by which deforestation may cause population declines in the face of climate change," said Ofir Levy, a zoologist and Musselman's collaborator at Tel Aviv University. "The decline in lizards can lead to a cascading effect as they are an important part of almost every ecological system."

Despite international pledges to halt deforestation, tree clearing continues to happen globally. From 2001 to 2022, about 459 million hectares, or 12%, of global tree cover disappeared.

"Deforestation is a worldwide problem, and our conclusions can help decision-makers on other continents in designing conservation and habitat restoration programs that consider climate change," said Omer Zlotnick, the paper's first author and a Ph.D. student at Tel Aviv University.

Lizard populations are already at risk because of climate change. In one study, scientists estimated that 54% of lizard populations in Mexico would go extinct by 2080 because of their inability to adapt to the rapidly warming planet.

Deforestation would further exacerbate the threat by taking away these animals' refuges.

Read more at Science Daily

Oldest known fossilized skin is 21 million years older than previous examples

Researchers have identified a 3D fragment of fossilized skin that is at least 21 million years than previously described skin fossils. The skin, which belonged to an early species of Paleozoic reptile, has a pebbled surface and most closely resembles crocodile skin. It's the oldest example of preserved epidermis, the outermost layer of skin in terrestrial reptiles, birds, and mammals, which was an important evolutionary adaptation in the transition to life on land. The fossil is described on January 11 in the journal Current Biology along with several other specimens that were collected from the Richards Spur limestone cave system in Oklahoma.

"Every now and then we get an exceptional opportunity to glimpse back into deep time," says first author Ethan Mooney, a paleontology graduate student at the University of Toronto who worked on the project as an undergraduate with paleontologist Robert Reisz at the University of Toronto.

"These types of discoveries can really enrich our understanding and perception of these pioneering animals."

Skin and other soft tissues are rarely fossilized, but the researchers think that skin preservation was possible in this case because of the cave system's unique features, which included fine clay sediments that slowed decomposition, oil seepage, and a cave environment that was likely an oxygenless environment.

"Animals would have fallen into this cave system during the early Permian and been buried in very fine clay sediments that delayed the decay process," says Mooney.

"But the kicker is that this cave system was also an active oil seepage site during the Permian, and interactions between hydrocarbons in petroleum and tar are likely what allowed this skin to be preserved."

The skin fossil is tiny -- smaller than a fingernail. Microscopic examination undertaken by coauthor Tea Maho of the University of Toronto Mississauga revealed epidermal tissues, a hallmark of the skin of amniotes, the terrestrial vertebrate group that includes reptiles, birds, and mammals and which evolved from amphibian ancestors during the Carboniferous Period.

"We were totally shocked by what we saw because it's completely unlike anything we would have expected," says Mooney.

"Finding such an old skin fossil is an exceptional opportunity to peer into the past and see what the skin of some of these earliest animals may have looked like."

The skin shares features with ancient and extant reptiles, including a pebbled surface similar to crocodile skin, and hinged regions between epidermal scales that resemble skin structures in snakes and worm lizards.

However, because the skin fossil is not associated with a skeleton or any other remains, it is not possible to identify what species of animal or body region the skin belonged to.

The fact that this ancient skin resembles the skin of reptiles alive today shows how important these structures are for survival in terrestrial environments.

"The epidermis was a critical feature for vertebrate survival on land," says Mooney.

"It's a crucial barrier between the internal body processes and the harsh outer environment."

The researchers say that this skin may represent the ancestral skin structure for terrestrial vertebrates in early amniotes that allowed for the eventual evolution of bird feathers and mammalian hair follicles.

Read more at Science Daily

Ancient sea monster remains reveal oldest mega-predatory pliosaur

The fossils of a 170-million-year-old ancient marine reptile from the Age of Dinosaurs have been identified as the oldest-known mega-predatory pliosaur -- a group of ocean-dwelling reptiles closely related to the famous long-necked plesiosaurs. The findings are rare and add new knowledge to the evolution of plesiosaurs. The study has been published in the journal Scientific Reports.

The fossils were found 40 years ago in north-eastern France. An international team of palaeontologists from the Naturkunde-Museum Bielefeld in Germany, the Institute of Paleobiology of the Polish Academy of Sciences in Warsaw, Poland, the Natural History Museum in Luxembourg and The Museum of Evolution at Uppsala University in Sweden have now analysed them and identified them as a new pliosaur genus: Lorrainosaurus.

Pliosaurs were a type of plesiosaur with short necks and massive skulls. They appeared over 200 million years ago, but remained minor components of marine ecosystems until suddenly developing into enormous apex predators. The new study shows that this adaptive shift followed feeding niche differentiation and the global decline of other predatory marine reptiles over 170 million years ago.

Lorrainosaurus is the oldest large-bodied pliosaur represented by an associated skeleton. It had jaws over 1.3 m long with large conical teeth and a bulky 'torpedo-shaped' body propelled by four flipper-like limbs.

"Lorrainosaurus was one of the first truly huge pliosaurs. It gave rise to a dynasty of marine reptile mega-predators that ruled the oceans for around 80 million years," explains Sven Sachs, a researcher at the Naturkunde-Museum Bielefeld, who led the study.

This giant reptile probably reached over 6 m from snout to tail, and lived during the early Middle Jurassic period. Intriguingly, very little is known about plesiosaurs from that time.

"Our identification of Lorrainosaurus as one of the earliest mega-predatory pliosaurs demonstrates that these creatures emerged immediately after a landmark restructuring of marine predator ecosystems across the Early-to-Middle Jurassic boundary, some 175 to 171 million years ago. This event profoundly affected many marine reptile groups and brought mega-predatory pliosaurids to dominance over 'fish-like' ichthyosaurs, ancient marine crocodile relatives, and other large-bodied predatory plesiosaurs," adds Daniel Madzia from the Institute of Paleobiology of the Polish Academy of Sciences, who co-led the study.

Pliosaurs were some of the most successful marine predators of their time.

"Famous examples, such as Pliosaurus and Kronosaurus -- some of the world's largest pliosaurs -- were absolutely enormous with body-lengths exceeding 10 m. They were ecological equivalents of today's Killer whales and would have eaten a range of prey including squid-like cephalopods, large fish and other marine reptiles. These have all been found as preserved gut contents," said senior co-author Benjamin Kear, Curator of Vertebrate Palaeontology and Researcher in Palaeontology at The Museum of Evolution, Uppsala University.

The recovered bones and teeth of Lorrainosaurus represent remnants of what was once a complete skeleton that decomposed and was dispersed across the ancient sea floor by currents and scavengers.

"The remains were unearthed in 1983 from a road cutting near Metz in Lorraine, north-eastern France. Palaeontology enthusiasts from the Association minéralogique et paléontologique d'Hayange et des environs recognised the significance of their discovery and donated the fossils to the Natural History Museum in Luxembourg," said co-author Ben Thuy, Curator at the Natural History Museum in Luxembourg.

Other than a brief report published in 1994, the fossils of Lorrainosaurus remained obscure until this new study re-evaluated the finds. Lorrainosaurus indicates that the reign of gigantic mega-predatory pliosaurs must have commenced earlier than previously thought, and was locally responsive to major ecological changes affecting marine environments covering what is now western Europe during the early Middle Jurassic.

Read more at Science Daily

Whale-like filter-feeding discovered in prehistoric marine reptile

A remarkable new fossil from China reveals for the first time that a group of reptiles were already using whale-like filter feeding 250 million years ago.

New research by a team from China and the UK has shown details of the skull of an early marine reptile called Hupehsuchus that indicate it had soft structures such as an expanding throat region to allow it to engulf great masses of water containing shrimp-like prey, and baleen whale-like structures to filter food items as it swam forward.

The team also found that the Hupehsuchus skulls show the same grooves and notches along the edges of its jaws similar to baleen whales, which have keratin strips instead of teeth.

"We were amazed to discover these adaptations in such an early marine reptile," said Zichen Fang of the Wuhan Center of China Geological Survey, who led the research. "The hupehsuchians were a unique group in China, close relatives of the ichthyosaurs, and known for 50 years, but their mode of life was not fully understood."

"The hupesuchians lived in the Early Triassic, about 248 million years ago, in China and they were part of a huge and rapid re-population of the oceans," said Professor Michael Benton, a collaborator at the University of Bristol's School of Earth Sciences. "This was a time of turmoil, only three million years after the huge end-Permian mass extinction which had wiped out most of life. It's been amazing to discover how fast these large marine reptiles came on the scene and entirely changed marine ecosystems of the time."

"We discovered two new hupehsuchian skulls," said Professor Long Cheng, also of the Wuhan Center of China Geological Survey, who directed the project. "These were more complete than earlier finds and showed that the long snout was composed of unfused, straplike bones, with a long space between them running the length of the snout. This construction is only seen otherwise in modern baleen whales where the loose structure of the snout and lower jaws allows them to support a huge throat region that balloons out enormously as they swim forward, engulfing small prey."

Read more at Science Daily

Which came first: The reptile or the egg?

The earliest reptiles, birds and mammals may have borne live young, researchers from Nanjing University and University of Bristol have revealed.

Until now, the hard-shelled egg was thought to be the key to the success of the amniotes -- a group of vertebrates that undergo embryonic or fetal development within an amnion, a protective membrane inside the egg.

However, a fresh study of 51 fossil species and 29 living species which could be categorised as oviparous (laying hard or soft-shelled eggs) or viviparous (giving birth to live young) suggests otherwise.

The findings, published today in Nature Ecology & Evolution, show that all the great evolutionary branches of Amniota, namely Mammalia, Lepidosauria (lizards and relatives), and Archosauria (dinosaurs, crocodilians, birds) reveal viviparity and extended embryo retention in their ancestors.

Extended embryo retention (EER) is when the young are retained by the mother for a varying amount of time, likely depending on when conditions are best for survival.

While the hard-shelled egg has often been seen as one of the greatest innovations in evolution, this research implies it was EER that gave this particular group of animals the ultimate protection.

Professor Michael Benton from the Bristol's School of Earth Sciences explained: "Before the amniotes, the first tetrapods to evolve limbs from fishy fins were broadly amphibious in habits. They had to live in or near water to feed and breed, as in modern amphibians such as frogs and salamanders.

"When the amniotes came on the scene 320 million years ago, they were able to break away from the water by evolving waterproof skin and other ways to control water loss. But the amniotic egg was the key. It was said to be a 'private pond' in which the developing reptile was protected from drying out in the warm climates and enabled the Amniota to move away from the waterside and dominate terrestrial ecosystems."

Project Leader Professor Baoyu Jiang added: "This standard view has been challenged. Biologists had noticed many lizards and snakes display flexible reproductive strategy across oviparity and viviparity.

"Sometimes, closely related species show both behaviours, and it turns out that live-bearing lizards can flip back to laying eggs much more easily than had been assumed."

"Also, when we look at fossils, we find that many of them were live-bearers, including the Mesozoic marine reptiles like ichthyosaurs and plesiosaurs," said Dr Armin Elsler. "Other fossils, including a choristodere from the Cretaceous of China, described here, show the to-and-fro between oviparity and viviparity happened in other groups, not just in lizards."

Dr Joseph Keating explained: "EER is widespread among vertebrates today, where the developing young are retained by the mother for a lesser or greater span of time.

"EER is common and variable in lizards and snakes today. Their young can be released, either inside an egg or as little wrigglers, at different developmental stages, and there appears to be ecological advantages of EER, perhaps allowing the mothers to release their young when temperatures are warm enough and food supplies are rich."

Professor Benton concluded: "Our work, and that of many others in recent years, has consigned the classic 'reptile egg' model of the textbooks to the wastebasket.

"The first amniotes had evolved extended embryo retention rather than a hard-shelled egg to protect the developing embryo for a lesser or greater amount of time inside the mother, so birth could be delayed until environments become favourable.

Read more at Science Daily

Ancient herbivore's diet weakened teeth leading to eventual starvation, study suggests

A team of researchers from the University of Bristol have shed light on the life of the ancient reptile Rhynchosaur, which walked the earth between 250-225 million years ago, before being replaced by the dinosaurs.

Rhynchosaurs are a little-understood group of roughly sheep-sized ancient reptiles that thrived during the Triassic Period, a time of generally warm climates and tough vegetation.

In the new study, the researchers studied specimens found in Devon and used CT scanning to see how the teeth wore down as they fed, and how new teeth were added at the backs of the tooth rows as the animals grew in size.

The findings, published today in Palaeontology, show that these early herbivores likely eventually starved to death in old age, the vegetation taking its toll on their teeth.

"I first studied the rhynchosaurs years ago," said team-leader Professor Mike Benton from Bristol's School of Earth Sciences, "and I was amazed to find that in many cases they dominated their ecosystems. If you found one fossil, you found hundreds. They were the sheep or antelopes of their day, and yet they had specialized dental systems that were apparently adapted for dealing with masses of tough plant food."

Dr Rob Coram, who discovered the Devon fossils, said: "The fossils are rare, but occasionally individuals were entombed during river floods. This has made it possible to put together a series of jaw bones of rhynchosaurs that ranged in age from quite young, maybe even babies, through adults, and including one particularly old animal, a Triassic old-timer whose teeth had worn right down and probably struggled to get enough nutrition each day."

"Comparing the sequence of fossils through their lifetime, we could see that as the animals aged, the area of the jaws under wear at any time moved backwards relative to the front of the skull, bringing new teeth and new bone into wear," said Thitiwoot Sethapanichsakul who studied the jaws as part of his MSc in Palaeobiology. "They were clearly eating really tough food such as ferns, that wore the teeth down to the bone of the jaw, meaning that they were basically chopping their meals by a mix of teeth and bone."

"Eventually, though, after a certain age -- we're not sure quite how many years -- their growth slowed down and the area of wear was fixed and just got deeper and deeper," added Dr Coram. "It's like elephants today -- they have a fixed number of teeth that come into use from the back, and after the age of seventy or so they're on their last tooth, and then that's that.

"We don't think the rhynchosaurs lived that long, but their plant food was so testing that their jaws simply wore out and presumably they eventually starved to death."

The rhynchosaurs were an important part of the ecosystems on land during the Triassic, when life was recovering from the world's greatest mass extinction, at the end of the preceding Permian Period. These animals were part of this recovery and setting the scene for new types of ecologies when first dinosaurs, and later mammals became dominant, as the modern world was being slowly constructed.

Read more at Science Daily

Fossil of mosasaur with bizarre 'screwdriver teeth' found in Morocco

Scientists have discovered a new species of mosasaur, a sea-dwelling lizard from the age of the dinosaurs, with strange, ridged teeth unlike those of any known reptile. Along with other recent finds from Africa, it suggests that mosasaurs and other marine reptiles were evolving rapidly up until 66 million years ago, when they were wiped out by an asteroid along with the dinosaurs and around 90% of all species on Earth.

The new species, Stelladens mysteriosus, comes from the Late Cretaceous of Morocco and was around twice the size of a dolphin.

It had a unique tooth arrangement with blade-like ridges running down the teeth, arranged in a star-shaped pattern, reminiscent of a cross-head screwdriver.

Most mosasaurs had two bladelike, serrated ridges on the front and back of the tooth to help cut prey, however Stelladens had anywhere from four to six of these blades running down the tooth.

"It's a surprise," said Dr Nick Longrich from the Milner Centre for Evolution at the University of Bath, who led the study. "It's not like any mosasaur, or any reptile, even any vertebrate we've seen before."

Dr Nathalie Bardet, a marine reptile specialist from the Museum of Natural History in Paris, said: "I've worked on the mosasaurs of Morocco for more than 20 years, and I'd never seen anything like this before -- I was both perplexed and amazed!"

That several teeth were found with the same shape suggests their strange shape was not the result of a pathology or a mutation.

The unique teeth suggest a specialised feeding strategy, or a specialised diet, but it remains unclear just what Stelladens ate.

Dr Longrich said: "We have no idea what this animal was eating, because we don't know of anything similar either alive today, or from the fossil record.

"It's possible it found a unique way to feed, or maybe it was filling an ecological niche that simply doesn't exist today. The teeth look like the tip of a Phillips-head screwdriver, or maybe a hex wrench.

"So what's it eating? Phillips head screws? IKEA furniture? Who knows."

The teeth were small, but stout and with wear on the tips, which seemed to rule out soft-bodied prey. The teeth weren't strong enough to crush heavily armoured animals like clams or sea urchins, however.

"That might seem to suggest it's eating something small, and lightly armoured -- thin-shelled ammonites, crustaceans, or bony fish -- but it's hard to know," said Longrich. "There were weird animals living in the Cretaceous- ammonites, belemnites, baculites -- that no longer exist. It's possible this mosasaur ate something, and occupied a niche, that simply doesn't exist anymore, and that might explain why nothing like this is ever seen again.

"Evolution isn't always predictable. Sometimes it goes off in a unique direction, and something evolves that's never been seen before, and then it never evolves again."

The mosasaurs lived alongside dinosaurs but weren't dinosaurs. Instead, they were giant lizards, relatives of Komodo dragons, snakes, and iguanas, adapted for a life at sea.

Mosasaurs evolved around 100 million years ago, and diversified up to 66 million years ago, when a giant asteroid hit the Yucatan Peninsula in Mexico, plunging the world into darkness.

Although scientists have debated the role of environmental changes towards the end of the Cretaceous in the extinction, Stelladens, along with recent discoveries from of Morocco, suggests that mosasaurs were evolving rapidly up to the very end -- they went out at their peak, rather than fading away.

The new study shows that even after years of work in the Cretaceous of Morocco, new species are continuing to be discovered. The reason may be that most species are rare.

The authors of the study predict that in a very diverse ecosystem, it may take decades to find all of the rare species.

"We're not even close to finding everything in these beds," said Longrich, "This is the third new species to appear, just this year. The amount of diversity at the end of the Cretaceous is just staggering."

Nour-Eddine Jalil, a professor at the Natural History Museum and a researcher at Univers Cadi Ayyad in Morocco, said: "The fauna has produced an incredible number of surprises -- mosasaurs with teeth arranged like a saw, a turtle with a snout in the form of snorkel, a multitude of vertebrates of various shapes and sizes, and now a mosasaur with star-shaped teeth.

Read more at Science Daily

Swimming secrets of prehistoric reptiles unlocked by new study

Some of the most extraordinary body transformations in evolution have occurred in animals that adapted to life in water from land-living ancestors, such as modern whales, turtles and seals. During the Mesozoic, from 252 to 66 million years ago, while the dinosaurs stomped about on land, many groups of reptiles took to the seas, such as the iconic ichthyosaurs, plesiosaurs, crocodiles and mosasaurs.

In a new paper, published in the journal Palaeontology, a Bristol team of palaeobiologists used state-of-the-art statistical methods to perform a large-scale quantitative study, the first of its kind, on the locomotion of Mesozoic marine reptiles.

The researchers collected measurements from 125 fossilised skeletons, and used these to explore changes in swimming styles within lineages and through time, discovering that there was no explosive radiation at the beginning of the Mesozoic, but a gradual diversification of locomotory modes, which peaked in the Cretaceous period.

Lead author Dr Susana Gutarra of Bristol's School of Earth Sciences said: "Changes in anatomy in land-to-sea transitions are intimately linked to the evolution of swimming. For example, sea lions' flippers have relatively short forearm and large hands, very different from the walking legs of their ancestors. The rich fossil record of Mesozoic marine reptiles provided great opportunity to study these transitions at a large scale."

Co-author Beatrice Heighton, said: "We included measurements from living aquatic animals, such as otters, seals and turtles, of which we know their swimming behaviour. This is very important to provide a functional reference for the ancient species, with unknown swimming modes."

In the aftermath of the end-Permian extinction, about 250 million years ago, various groups of reptiles became aquatic hunters, populating the early Mesozoic seas.

Co-author Dr Tom Stubbs said: "After this devastating event, there was a gradual diversification of locomotory modes, which contrasts with the rapid radiation described previously for feeding strategies. This is fascinating because it suggests a 'head-first' pattern of evolution in certain lineages."

This paper sheds light into the swimming of specific groups. Dr Ben Moon explained: "Ichthyosaurs were highly specialised for aquatic locomotion from very early in their evolution. This includes their close relatives, the hupehsuchians, which had a morphology unlike any other known aquatic tetrapod. Further, we see overlap between mosasaurs and ichthyosaurs, which is indicative that mosasaurs evolved a swimming mode by oscillating flukes, different from the eel-like body undulation suggested in the past.

"In contrast, we don't find evidence of convergence between ichthyosaurs and metriorhynchids (the highly aquatic crocodyliform thalattosuchians). This group retained quite primitive-looking hindlimbs, which seems incompatible with swimming by fluke oscillation."

This study also delves into the evolution of size, a feature related to locomotion, animal physiology and ocean productivity. Professor Mike Benton said: "We know that transition to life in water is usually accompanied by an increase in body mass, as seen in cetaceans, and one of our previous studies shows that large sizes benefit aquatic animals in reducing the mass-specific costs of drag. Thus, it was essential to explore this trait in the wider ensemble of Mesozoic marine reptiles."

Dr Gutarra added: "Body size follows a similar trend to the diversification of locomotory modes, and the widest spread of body size also occurred in the Cretaceous, confirming a strong connection between the two. The rate of increase and the maximum limits to body size seems to vary a lot between groups. This is a fascinating observation. We need to explore further what factors influence and limit the increase in body mass in each group."

Read more at Science Daily

Vocal communication originated over 400 million years ago

The use of vocalizations as a resource for communication is common among several groups of vertebrates: singing birds, croacking frogs, or barking dogs are some well-known examples. These vocalizations play a fundamental role in parental care, mate attraction and various other behaviors. Despite its importance, little is known about when and at what stage in the evolutionary history of vertebrates this behavior first appeared. Comparative analyses can provide insights into the evolutionary origin of acoustic communication, but they are often plagued by missing information from key groups that have not been broadly studied.

Acoustic abilities are widespread in land vertebrates

An international research team led by the University of Zurich (UZH) has therefore focused on species that have never been accessed before. Their study includes evidence for 53 species of four major clades of land vertebrates -- turtles, tuataras, caecilians and lungfishes -- in the form of vocal recordings and contextual behavioral information accompanying sound production. "This, along with a broad literature-based dataset including 1800 different species covering the entire spectrum shows that vocal communication is not only widespread in land vertebrates, but also evidence acoustic abilities in several groups previously considered non-vocal," says first author Gabriel Jorgewich-Cohen, PhD student at the Paleontological Institute and Museum of UZH. Many turtles, for example, which were thought to be mute are in fact showing broad and complex acoustic repertoires.

Last common ancestor lived about 407 million years ago

To investigate the evolutionary origins of acoustic communication in vertebrates, the researchers combined relevant data on the vocalization abilities of species like lizards, snakes, salamanders, amphibians, and dipnoi with phylogenetic trait reconstruction methods. Combined with data of well-known acoustic clades like mammals, birds, and frogs, the researchers were able to map vocal communication in the vertebrate tree of life. "We were able to reconstruct acoustic communication as a shared trait among these animals, which is at least as old as their last common ancestor that lived approximately 407 million years before present," explains Marcelo Sánchez, who led the study.

Read more at Science Daily

Triassic specimen found to be early relative of pterosaurs a century after its discovery

A new study of a tiny Triassic fossil reptile first discovered over 100 years ago in the north east of Scotland has revealed it to be a close relative of the species that would become pterosaurs -- iconic flying reptiles of the age of the dinosaurs.

The research, published in Nature, was carried out by a team of scientists led by Dr Davide Foffa, Research Associate at National Museums Scotland, and now a Research Fellow at the University of Birmingham. Working together with colleagues at Virginia Tech, the team used Computed Tomography (CT) to provide the first accurate whole skeleton reconstruction of Scleromochlus taylori.

The results reveal new anatomical details that conclusively identify it as a close pterosaur relative. It falls within a group known as Pterosauromorpha, comprising an extinct group of reptiles called lagerpetids together with pterosaurs.

Living approximately 240 -210 million years ago, lagerpetids were a group of relatively small (cat or small dog-sized) active reptiles. Schleromochlus was smaller still at under 20 centimetres in length. The results support the hypothesis that the first flying reptiles evolved from small, likely bipedal ancestors.

The finding settles a century-long debate. There had previously been disagreement as to whether the reptile, Scleromochlus, represented an evolutionary step in the direction of pterosaurs, dinosaurs or else some other reptilian offshoot.

The fossil of Scleromochlus is poorly preserved in a block of sandstone, which has made it difficult to study in sufficient detail to properly identify its anatomical features. The fossil is one of a group known as the Elgin Reptiles, comprising Triassic and Permian specimens found in the sandstone of the Morayshire region of north east Scotland around the town of Elgin.

The specimens are held mostly in the collections of National Museums Scotland, Elgin Museum and the Natural History Museum. The latter holds Scleromochlus, which was originally found at Lossiemouth.

Dr Foffa said: "It's exciting to be able to resolve a debate that's been going on for over a century, but it is far more amazing to be able to see and understand an animal which lived 230 million years ago and its relationship with the first animals ever to have flown. This is another discovery which highlights Scotland's important place in the global fossil record, and also the importance of museum collections that preserve such specimens, allowing us to use new techniques and technologies to continue to learn from them long after their discovery."

Professor Paul Barrett at the Natural History Museum said: "The Elgin reptiles aren't preserved as the pristine, complete skeletons that we often see in museum displays. They're mainly represented by natural moulds of their bone in sandstone and -- until fairly recently -- the only way to study them was to use wax or latex to fill these moulds and make casts of the bones that once occupied them. However, the use of CT scanning has revolutionized the study of these difficult specimens and has enabled us to produce far more detailed, accurate and useful reconstructions of these animals from our deep past."

Professor Sterling Nesbitt at Virgina Tech said: "Pterosaurs were the first vertebrates to evolve powered flight and for nearly two centuries, we did not know their closest relatives. Now we can start filling in their evolutionary history with the discovery of tiny close relatives that enhance our knowledge about how they lived and where they came from"

Read more at Science Daily

Changes in the tree canopy facilitated the evolution of the first-ever gliding reptile

Researchers have run through near-perfect fossils of the World's first gliding reptile with a fine-toothed comb and untangled hitherto unknown facets to discover it was a change in tree canopy which likely facilitated such flight in these creatures.

Since the first fossils of Coelurosauravus elivensis were discovered in 1907, there has been spirited debate over how the animal actually lived during the Late Permian Period -- between 260 million to 252 million years ago -- and how its unique body parts fit together.

By piecing together enough fossils to create a near-perfect skeletal reconstruction, new research provides fresh insights into the tetrapod's morphology and its habits; and crucially establishes how it became the first-known reptile to glide.

The answer to the latter derives from the canopy of the forestry in which this unusual creature lived in -- suggest experts from the French National Museum of Natural History, in Paris (or Muséum national d'Histoire naturelle) and the Staatliches Museum für Naturkunde Karlsruhe, in Germany.

Explaining their findings, today, in the peer-reviewed Journal of Vertebrate Paleontology, lead author Valentin Buffa, from the Centre de Recherche en Paléontologie -- Paris at the French Natural History Museum, states: "Pennsylvanian forests, while taxonomically and vertically heterogeneous, had rather open canopy strata with spatially separated arborescent taxa resulting in little crown overlap. In contrast, Cisularian forests show evidence of denser communities suggestive of more continuous canopy strata. Such change in forest structure could explain why no gliders have been reported prior to weigeltisaurids although several arboreal or scansorial amniotes have been described from Pennsylvanian and Cisularian deposits.

"These dragons weren't forged in mythological fire -- they simply needed to get from place to place. As it turned out, gliding was the most efficient mode of transport and here, in this new study, we see how their morphology enabled this."

The team examined three known fossils of C. elivensis, as well as a number of related specimens -- all belonging to the family Weigeltisauridae. Their research focused on the postcranial portion -- the body, including the torso, limbs, and remarkable gliding apparatus, known as the patagium. The latter is the membranous flap spanning the forelimbs and hindlimbs, also found in such living animals as flying squirrels, sugar gliders, and colugos.

Previous analysis of the reptile had assumed that its patagium was supported by bones that extended from the ribs, as they do in modern Draco species of Southeast Asia -- which, to this day, amazes observers with its gliding flights between the rainforest trees it inhabits.

However, this thorough new examination suggests that the patagium of C. elivensis either extended from the gastralia -- an arrangement of bones in the skin that covers the belly of some reptiles, including crocodilians and dinosaurs -- or from the musculature of the trunk. This would mean that the gliding apparatus sat lower on the abdomen than it does in modern gliding lizards.

Combining this finding with others derived from the bone structure observed in the fossils, the researchers came up with a more refined vision of how this agile creature moved through its arboreal habitat.

"Sharp, curved claws and compressed body form support the idea that was perfectly adapted to moving vertically up tree trunks. The similarity in length of the forelimbs and hindlimbs further indicate that it was an expert climber -- their proportional length assisted it in remaining close to the tree's surface, preventing it from pitching and losing its balance. Its long, lean body and whiplike tail, also seen in contemporary arboreal reptiles, further supports this interpretation," adds Valentin Buffa.

Read more at Science Daily

Hot-blooded T. rex and cold-blooded Stegosaurus: Chemical clues reveal dinosaur metabolisms

For decades, paleontologists have debated whether dinosaurs were warm-blooded, like modern mammals and birds, or cold-blooded, like modern reptiles. Knowing whether dinosaurs were warm- or cold-blooded could give us hints about how active they were and what their everyday lives were like, but the methods to determine their warm- or cold-bloodedness -- how quickly their metabolisms could turn oxygen into energy -- were inconclusive. But in a new paper in Nature, scientists are unveiling a new method for studying dinosaurs' metabolic rates, using clues in their bones that indicated how much the individual animals breathed in their last hour of life.

"This is really exciting for us as paleontologists -- the question of whether dinosaurs were warm- or cold-blooded is one of the oldest questions in paleontology, and now we think we have a consensus, that most dinosaurs were warm-blooded," says Jasmina Wiemann, the paper's lead author and a postdoctoral researcher at the California Institute of Technology.

"The new proxy developed by Jasmina Wiemann allows us to directly infer metabolism in extinct organisms, something that we were only dreaming about just a few years ago. We also found different metabolic rates characterizing different groups, which was previously suggested based on other methods, but never directly tested," says Matteo Fabbri, a postdoctoral researcher at the Field Museum in Chicago and one of the study's authors.

People sometimes talk about metabolism in terms of how easy it is for someone to stay in shape, but at its core, "metabolism is how effectively we convert the oxygen that we breathe into chemical energy that fuels our body," says Wiemann, who is affiliated with Yale University and the Natural History Museum of Los Angeles County.

Animals with a high metabolic rate are endothermic, or warm-blooded; warm-blooded animals like birds and mammals take in lots of oxygen and have to burn a lot of calories in order to maintain their body temperature and stay active. Cold-blooded, or ectothermic, animals like reptiles breathe less and eat less. Their lifestyle is less energetically expensive than a hot-blooded animal's, but it comes at a price: cold-blooded animals are reliant on the outside world to keep their bodies at the right temperature to function (like a lizard basking in the sun), and they tend to be less active than warm-blooded creatures.

With birds being warm-blooded and reptiles being cold-blooded, dinosaurs were caught in the middle of a debate. Birds are the only dinosaurs that survived the mass extinction at the end of the Cretaceous, but dinosaurs (and by extension, birds) are technically reptiles -- outside of birds, their closest living relatives are crocodiles and alligators. So would that make dinosaurs warm-blooded, or cold-blooded?

Scientists have tried to glean dinosaurs' metabolic rates from chemical and osteohistological analyses of their bones. "In the past, people have looked at dinosaur bones with isotope geochemistry that basically works like a paleo-thermometer," says Wiemann -- researchers examine the minerals in a fossil and determine what temperatures those minerals would form in. "It's a really cool approach and it was really revolutionary when it came out, and it continues to provide very exciting insights into the physiology of extinct animals. But we've realized that we don't really understand yet how fossilization processes change the isotope signals that we pick up, so it is hard to unambiguously compare the data from fossils to modern animals."

Another method for studying metabolism is growth rate. "If you look at a cross section of dinosaur bone tissue, you can see a series of lines, like tree rings, that correspond to years of growth," says Fabbri. "You can count the lines of growth and the space between them to see how fast the dinosaur grew. The limit relies on how you transform growth rate estimates into metabolism: growing faster or slower can have more to do with the animal's stage in life than with its metabolism, like how we grow faster when we're young and slower when we're older."

The new method proposed by Wiemann, Fabbri, and their colleagues doesn't look at the minerals present in bone or how quickly the dinosaur grew. Instead, they look at one of the most basic hallmarks of metabolism: oxygen use. When animals breathe, side products form that react with proteins, sugars, and lipids, leaving behind molecular "waste." This waste is extremely stable and water-insoluble, so it's preserved during the fossilization process. It leaves behind a record of how much oxygen a dinosaur was breathing in, and thus, its metabolic rate.

The researchers looked for these bits of molecular waste in dark-colored fossil femurs, because those dark colors indicate that lots of organic matter are preserved. They examined the fossils using Raman and Fourier-transform infrared spectroscopy -- "these methods work like laser microscopes, we can basically quantify the abundance of these molecular markers that tell us about the metabolic rate," says Wiemann. "It is a particularly attractive method to paleontologists, because it is non-destructive."

The team analyzed the femurs of 55 different groups of animals, including dinosaurs, their flying cousins the pterosaurs, their more distant marine relatives the plesiosaurs, and modern birds, mammals, and lizards. They compared the amount of breathing-related molecular byproducts with the known metabolic rates of the living animals and used those data to infer the metabolic rates of the extinct ones.

The team found that dinosaurs' metabolic rates were generally high. There are two big groups of dinosaurs, the saurischians and the ornithischians -- lizard hips and bird hips. The bird-hipped dinosaurs, like Triceratops and Stegosaurus, had low metabolic rates comparable to those of cold-blooded modern animals. The lizard-hipped dinosaurs, including theropods and the sauropods -- the two-legged, more bird-like predatory dinosaurs like Velociraptor and T. rex and the giant, long-necked herbivores like Brachiosaurus -- were warm- or even hot-blooded. The researchers were surprised to find that some of these dinosaurs weren't just warm-blooded -- they had metabolic rates comparable to modern birds, much higher than mammals. These results complement previous independent observations that hinted at such trends but could not provide direct evidence, because of the lack of a direct proxy to infer metabolism.

These findings, the researchers say, can give us fundamentally new insights into what dinosaurs' lives were like.

"Dinosaurs with lower metabolic rates would have been, to some extent, dependent on external temperatures," says Wiemann. "Lizards and turtles sit in the sun and bask, and we may have to consider similar 'behavioral' thermoregulation in ornithischians with exceptionally low metabolic rates. Cold-blooded dinosaurs also might have had to migrate to warmer climates during the cold season, and climate may have been a selective factor for where some of these dinosaurs could live."

On the other hand, she says, the hot-blooded dinosaurs would have been more active and would have needed to eat a lot. "The hot-blooded giant sauropods were herbivores, and it would take a lot of plant matter to feed this metabolic system. They had very efficient digestive systems, and since they were so big, it probably was more of a problem for them to cool down than to heat up." Meanwhile, the theropod dinosaurs -- the group that contains birds -- developed high metabolisms even before some of their members evolved flight.

"Reconstructing the biology and physiology of extinct animals is one of the hardest things to do in paleontology. This new study adds a fundamental piece of the puzzle in understanding the evolution of physiology in deep time and complements previous proxies used to investigate these questions. We can now infer body temperature through isotopes, growth strategies through osteohistology, and metabolic rates through chemical proxies," says Fabbri.

In addition to giving us insights into what dinosaurs were like, this study also helps us better understand the world around us today. Dinosaurs, with the exception of birds, died out in a mass extinction 65 million years ago when an asteroid struck the Earth. "Having a high metabolic rate has generally been suggested as one of the key advantages when it comes to surviving mass extinctions and successfully radiating afterwards," says Wiemann -- some scientists have proposed that birds survived while the non-avian dinosaurs died because of the birds' increased metabolic capacity. But this study, Wiemann says, helps to show that this isn't true: many dinosaurs with bird-like, exceptional metabolic capacities went extinct.

Read more at Science Daily

Large bodies helped extinct marine reptiles with long necks swim, new study finds

Scientists at the University of Bristol have discovered that body size is more important than body shape in determining the energy economy of swimming for aquatic animals.

This study, published today in Communications Biology, shows that big bodies help overcome the excess drag produced by extreme morphology, debunking a long-standing idea that there is an optimal body shape for low drag.

One important finding of this research is that the large necks of extinct elasmosaurs did add extra drag, but this was compensated by the evolution of large bodies.

Tetrapods or 'four-limbed vertebrates', have repeatedly returned to the oceans over the last 250 million years, and they come in many shapes and sizes, ranging from streamlined modern whales over 25 meters in length, to extinct plesiosaurs, with four flippers and extraordinarily long necks, and even extinct fish-shaped ichthyosaurs.

Dolphins and ichthyosaurs have similar body shapes, adapted for moving fast through water producing low resistance or drag. On the other hand, plesiosaurs, who lived side by side with the ichthyosaurs in the Mesozoic Era, had entirely different bodies. Their enormous four flippers which they used to fly underwater, and variable neck lengths, have no parallel amongst living animals. Some elasmosaurs had really extreme proportions, with necks up to 20 feet (6 metres) long. These necks likely helped them to snap up quick-moving fish, but were also believed to make them slower.

Until now, it has not been clear how shape and size influenced the energy demands of swimming in these diverse marine animals. Palaeobiologist Dr Susana Gutarra Díaz of Bristol's School of Earth Sciences and the National History Museum of London who led the research, explained: "To test our hypotheses, we created various 3D models and performed computer flow simulations of plesiosaurs, ichthyosaurs and cetaceans. These experiments are performed on the computer, but they are like water tank experiments."

Dr Colin Palmer, an engineer involved in the project said: "We showed that although plesiosaurs did experience more drag than ichthyosaurs or whales of equal mass because of their unique body shape, these differences were relatively minor. We found that when size is taken into account, the differences between groups became much less than the shape differences. We also show that the ratio of body length to diameter, which is widely used to classify these aquatic animals as more or less efficient, is not a good indicator of low drag."

Dr Gutarra Díaz said, "We were also particularly interested in the necks of elasmosaurs and so, we created hypothetical 3D models of plesiosaurs with various lengths of necks. Simulations of these models reveal that past a certain point, the neck adds extra drag, which potentially would make swimming costly. This 'optimal' neck limit lies around twice the length of the trunk of the animal."

Dr Benjamin Moon, another collaborator and expert on marine reptiles, continued: "When we examined a large sample of plesiosaurs modelled on really well preserved fossils at their real sizes, it turns out that most plesiosaurs had necks below this high-drag threshold, within which neck can get longer or shorter without increasing drag. But more interestingly, we showed that plesiosaurs with extremely long necks also had evolved very large torsos, and this compensated for the extra drag!"

Dr Tom Stubbs, another co-author summarised: "This study shows that, in contrast with prevailing popular knowledge, very long necked plesiosaurs were not necessarily slower swimmers than ichthyosaurs and whales, and this is in part thanks to their large bodies. We found that in elasmosaurs, neck proportions changed really fast. This confirms that long necks were advantageous for elasmosaurs in hunting, but they could not exploit this adaptation until they became large enough to offset the cost of high drag on their bodies."

Read more at Science Daily

Extinct reptile discovery reveals earliest origins of human teeth, study finds

A new extinct reptile species has shed light on how our earliest ancestors became top predators by modifying their teeth in response to environmental instability around 300 million years ago.

In findings published in Royal Society Open Science, researchers at the University of Bristol have discovered that this evolutionary adaptation laid the foundations for the incisor, canine and molar teeth that all mammals -- including humans -- possess today.

Shashajaia is one of the most primitive members of a group called the Sphenacodontoidea, which includes the famous sail-backed Dimetrodon, and mammal-like reptiles known as therapsids, which eventually evolved into mammals. It is remarkable for its age and anatomy, possessing a very unique set of teeth that set it apart from other synapsids -- meaning the animal lineage that mammals belong to -- of the time.

Dr Suresh Singh of the School of Earth Sciences explained: "The teeth show clear differentiation in shape between the front and back of the jaw, organised into distinct regions. This is the basic precursor of what mammals have today -- incisors and canines up front, with molars in the back. This is the oldest record of such teeth in our evolutionary tree."

The novel dentition of Shashajaia demonstratesthat large, canine-like differentiated teeth were present in synapsids by the Late Carboniferous period -- a time famous for giant insects and the global swampy rainforests that produced much of our coal deposits.

By analytically comparing the tooth variation observed in Shashajaia with other synapsids, the study suggests that distinctive, specialised teeth likely emerged in our synapsid ancestors as a predatory adaptation to help them catch prey at a time when global climate change approximately 300 million years ago saw once-prevalent Carboniferous wetlands replaced by more arid, seasonal environments. These new, more changeable conditions brought a change in the availability and diversity of prey.

Lead author Dr Adam Huttenlocker of the University of Southern California said: "Canine-like teeth in small sphenacodonts like Shashajaia might have facilitated a fast, raptorial bite in riparian habitats where a mix of terrestrial and semi-aquatic prey could be found in abundance."

The new reptile is one of the oldest synapsids. It was named "Shashajaia bermani," which translates as Berman's bear heart, to honour the 51-year career of veteran palaeontologist, Dr David Berman of the Carnegie Museum of Natural History, as well as the local Navajo people of the discovery site within the Bears Ears National Monument, Utah.

Dr Singh said: "The study is a testament to Dr Berman who originally discovered the fossil site in 1989, and his decades of work on synapsids and other early tetrapods from the Bears Ears region of Utah which helped to justify the Bears Ears National Monument in 2016."

The site is located within an area known as the Valley of the Gods and is of huge importance to palaeontologists.

Read more at Science Daily

Mammals’ noses come from reptiles’ jaws

New examinations of skeletons and animal embryos have allowed researchers to discover how mammals developed protruding, flexible noses. This study contributes to uncovering the origin of mammals' strong sense of smell and creates the potential for new animal models, like chickens or frogs, that are often used in lab experiments to investigate facial development disorders such as cleft palate.

The traditional scientific understanding of facial evolution is that both mammalian and reptilian jaws develop in almost the same way. Even though mammals have a unique nose, the evolution of this structure has remained unknown.

"Existing fossils of four-legged animals, both reptilian and mammalian ancestors, have the same number of upper jaw bones. It's very easy to think that the bones are the same, but now we can study embryos and track cellular development to study these bones in much greater detail," explained postdoctoral researcher Hiroki Higashiyama, who studies evolutionary development at the University of Tokyo Graduate School of Medicine. The research, recently published in Proceedings of the National Academy of Sciences, is the first to examine the evolution of facial structure using cellular studies comparing multiple embryos of multiple species.

Higashiyama and his colleagues in the laboratory of Professor Hiroki Kurihara designed experiments to track facial development in embryos of different species, including birds (chickens), reptiles (geckos) and mammals (mice). They focused on a group of cells known as the facial prominences in embryos that produce the physical structures of the face. Researchers stained the cells to track them as they moved and grew. A group of cells called the frontonasal prominence forms the jaw tip in reptiles, but becomes the protruding nose in mammals. Mammals' jaw tips form instead from a separate group of cells called the maxillary prominence.

Using this new perspective from their cellular experiments, researchers then examined fossil specimens.

As species' ancestors accumulated more physical and genetic differences, the bone at the tip of reptiles' upper jaw, the premaxilla, became smaller and migrated upwards and the bone that was behind it, the septomaxilla, became larger and moved forwards to become mammals' jaw tip. Researchers say that the facial bones of egg-laying mammals, like the Australian platypus and echidna, provide additional living examples of transitional bone structures from the evolutionarily older reptile model to the more recently evolved mammalian structure.

This separation of the nose and jaw gives mammals their unique ability to "sniff," using muscles to flare the nostrils and deeply inhale odors from the environment.

"This finding is a key innovation in the evolution of our and other mammals' motile nose, which contributes to mammals' highly sensitive sense of smell," said Higashiyama.

Distinguishing and recognizing so many odors may have also helped mammals develop larger, more complex brains than earlier ancestor species.

The recent research has provided physical evidence of the evolutionary shift in premaxilla and septomaxilla arrangement, but separate studies will be needed to identify the genetic causes.

"Now we know the composition of facial prominences and embryonic development in multiple species, so we can compare facial development disorders in chickens or frogs to humans. We have mainly just improved textbook knowledge for now, but in the future, these animal models will be a practical application of our studies," said Higashiyama.

Read more at Science Daily

Plant-eating lizards on the cusp of tooth evolution

Researchers at the Universities of Helsinki and Lyon and the Geological Survey of Finland found that complex teeth, a hallmark of mammals, also evolved several times in reptiles, prompting the evolutionary success of plant-eating lizards. However, contrary to mammals their tooth evolution was not unidirectional.

The study, published in Nature Communications, reveals that several lizard groups evolved teeth with multiple tips ("cusps") that allowed new plant-based diets and higher speciation rates -- that is, how fast new species appear. Surprisingly, tooth evolution was more flexible in lizards and snakes than mammals, revealing a more nuanced view of tooth and dietary evolutionary adaptations in vertebrates.

Tooth shape is closely linked with diet

Scientists have richly documented the connection of tooth shape and diet in mammals, showing very diverse teeth fuelled their evolutionary success. But what about other toothed animals? The authors chose to study squamates, the group including lizards and snakes. "The teeth of squamates have received limited attention, even though they twice outnumber mammals in species numbers, and span many habitats and geographic ranges," remarks Nicolas Di-Poï, Associate Professor at the Institute of Biotechnology, University of Helsinki.

The researchers performed comparative analyses on tooth shape and diet data for more than 500 living and fossil species. They found the ancestor to all snakes and lizards had simple peg-like teeth and fed on insects. Later, complex teeth bearing multiple cusps -- similar to those of early mammals -- evolved multiple times independently in different lizard lineages. The appearance of multiple-cusped teeth allowed some lizard groups to evolve more plant-rich diets, sometimes leading to even more complex teeth.

Lizards' teeth evolution took two directions

The team also found that complex teeth and plant consumption provided an evolutionary advantage, as both traits favoured the appearance of new species. However, many lizard lineages also lost complex teeth to re-evolve the ancestral simple tooth morphology. "This came as a complete surprise," says PhD candidate Fabien Lafuma from the University of Helsinki, "as complex teeth appear as a critical innovation for both squamates and mammals."

Read more at Science Daily

New fossil species represents ancient forerunner of most modern reptiles

Lizards and snakes are a key component of most terrestrial ecosystems on earth today. Along with the charismatic tuatara of New Zealand (a "living fossil" represented by a single living species), squamates (all lizards and snakes) make up the Lepidosauria -- the largest group of terrestrial vertebrates in the planet today with approximately 11,000 species, and by far the largest modern group of reptiles. Both squamates and tuataras have an extremely long evolutionary history. Their lineages are older than dinosaurs having originated and diverged from each other at some point around 260 million years ago. However, the early phase of lepidosaur evolution 260-150 million years ago, is marked by very fragmented fossils that do not provide much useful data to understand their early evolution, leaving the origins of this vastly diverse group of animals embedded in mystery for decades.

In a study published August 25 in Nature an international team of researchers describe a new species that represents the most primitive member of lepidosaurs, Taytalura alcoberi, found in the Late Triassic deposits of Argentina. Discovered by lead author Dr. Ricardo N. Martínez, Universidad Nacional de San Juan, Argentina, and curator at the Instituto y Museo de Ciencias Naturales, Taytalura is the first three-dimensionally preserved early lepidosaur fossil. It allowed scientists to infer with great confidence it's placement in the evolutionary tree of reptiles and aids in closing the gap of our knowledge of the origin and early evolution of lepidosaurs.

Martínez and co-author Dr. Sebastián Apesteguía, Universidad Maimónides, Buenos Aires, Argentina,conducted high-resolution CT scans of Taytalura which provided confirmation that it was something related to ancient lizards. They then contacted co-author Dr. Tiago R. Simões, postdoctoral fellow in The Department of Organismic and Evolutionary Biology, Harvard University, to help identify and analyze the fossil. Simões specializes in studying these creatures and in 2018 published the largest existing dataset to understand the evolution of the major groups of reptiles (living and extinct) in Nature.

"I knew the age and locality of the fossil and could tell by examining some of its external features that it was closely related to lizards, but it looked more primitive than a true lizard and that is something quite special," said Simões.

The researchers then contacted co-author Dr. Gabriela Sobral, Department of Palaeontology, Staatliches Museum für Naturkunde Stuttgart, Germany, to process the CT scan data. Sobral, a specialist in processing CT data, created a mosaic of colors for each bone of the skull allowing the team to understand the fossil's anatomy in high-detail resolution on a scale of only a few micrometers -- about the same thickness as a human hair.

With Sobral's data, Simões was able to apply a Bayesian evolutionary analysis to determine the proper placement of the fossil in the reptile dataset. Simões had recently applied the Bayesian method -- which was adapted from methods originally developed in epidemiology to study how viruses like COVID-19 evolve -- to precisely estimate the time and rates of anatomical evolution during the rise of tetrapods. The statistical analysis confirmed their suspicions that Taytalura was in fact the most primitive member of the lineage that eventually originated all lizards and snakes. "It's not even a lizard in the evolutionary tree," said Simões, "but it's the very next thing there, between true liizards and tuataras, and all other reptiles."

"This beautifully 3D preserved fossil is really an important finding. It is the most complete fossil representing the early stages of lepidosaur evolution that we have so far. All other known fossils are too incomplete, which makes it difficult to classify them for sure, but the complete and articulated nature of Taytalura makes its relationships much more certain," said Sobral.

Simões agreed, "Taytalura is a major point in the reptile tree of life that was previously missing. Because these fossils are so small they are very difficult to preserve in the fossil record. And what candidate fossils we do have are very fragmented and poorly preserved, so they don't provide as much useful data for analysis."

Taytalura's skull reveals that the first lepidosaurs looked substantially more like the tuataras than squamates, and therefore, that squamates represent a major deviation from this ancestral pattern. Further, it has a unique dentition, differing from the teeth found in any living or extinct group of lepidosaurs. "What our analyses tells us, besides some other anatomical traits that we could see on it, in the skull specifically, is that this sphenodontian body type, at least for the skull, is the ancestral pattern for lepidosaurs. The ancestral pattern seems to be more similar to tuataras," said Simões.

"Taytalura preserves a composition of features that we were not expecting to find in such an early fossil. For instance, it shows some features that we thought were exclusive for the tuatara group. On the other hand, it made us question how truly "primitive" certain lizard features are, and it will make scientists reconsider several points in the evolution of this group," said Sobral.

"The almost perfectly preserved Taytalura skull shows us details of how a very successful group of animals, including more than 10,000 species of snakes, lizards, and tuataras, originated," said Martínez. "But it also highlights the paleontological importance of the paleontological site of Ischigualasto Formation, known for preserving some of the most primitive dinosaurs known in the world. The extraordinary quality of preservation of the fossils at this site allowed something as fragile and tiny as this specimen to be preserved for 231 million years."

"Contrary to almost all fossils of Triassic lepidosaurs found in Europe, this is the first early lepidosaur found in South America, suggesting lepidosaurs were able to migrate across vastly distant geographic regions early in their evolutionary history," agreed Simões.

"We are accustomed to accept that the Mesozoic Era was an age of gigantic reptiles, enormous proto-mammals, and huge trees, and thus we commonly look for fossils that are visible at human height, just walking," said Apesteguía. "However, the largest part of the ancient ecosystem components was small, as today. There was a universe of fauna sneaking among bigger, clawed or hoofy paws. Taytalura teaches us that we were missing important information by looking not only for bigger animals, but for also thinking that the origin of lizards occurred only in the Northern Hemisphere as evidence seemed to support until now."

Read more at Science Daily

CT scan of an ancient reptile skull reveals little evolutionary change over 22 million years

A CT scan of the skull of a long-necked plesiosaur shows the cranial architecture of these long-extinct marine reptiles didn't evolve much over 22 million years that they lived during the Cretaceous time.

That's very unusual, said SMU paleontologist Louis Jacobs, an expert on prehistoric creatures and co-author of a study published in PLOS One.

"Basically, in anything except living fossils, you don't go 22 million years without evolving," said Jacobs, professor emeritus of Earth Sciences at SMU and president of ISEM at SMU.

Elasmosaurid plesiosaurs, lookalikes of the mythical Loch Ness monster, were the largest of the long-necked plesiosaurs, growing as long as 43 feet with half of that length deriving from their small heads and very long necks. Paleontologists from SMU (Southern Methodist University), as part of an international team called Projecto PaleoAngola, based their findings on a CT scan of the 71.5 million year old skull from a species of elasmosaurid called Cardiocorax mukulu.

This detailed 3D model allowed the paleontologists to compare the well-preserved skull of C. mukulu found in Angola to that of other species of elasmosaurids. They found that C. mukulu looked nearly identical to skulls that came from much older elasmosaurids, including one found at Cedar Hill, Texas, in 1931, whose 93-million-years old remains can be found at SMU's Shuler Museum of Paleontology.

"The skull shape, organization of muscles, and the shape and arrangement of the teeth largely reflect how an animal acquired prey," said co-author Michael J. Polcyn, research associate and director of SMU's Digital Earth Sciences Laboratory "The interesting aspect of Cardiocorax mukulu is that it appears that this animal's predecessors adopted a particular feeding style early in their evolutionary history, and then maintained the same basic skull structure for the next 22 million years"

It will take more research to pinpoint why elasmosaurids might have been different from other reptiles in their evolutionary journey.

Elasmosaurids lived during the Cretaceous Period, which spanned from 145 million years ago to 66 million years ago. They were predators, thriving on fish and other marine life. Projecto PaleoAngola paleontologists first discovered C. mukulu in Angola in 2015.

The lead author of the CT scan study is Miguel P. Marx, who will be starting a Ph.D. program at Lund University in Sweden later this month and was a researcher in SMU's Earth Science department during this study. Other co-authors include Jacobs and Polcyn of SMU.; OctávioMateus of Universidade Nova de Lisboa and Museu da Lourinhã, Portugal; Anne S. Schulp of the Naturalis Biodiversity Center and Utrecht University in the Netherlands; and A. Olímpio Gonçalves of the Universidade Agostinho Neto in Angola.

Skull found in the same area that yielded Smithsonian Museum exhibit

Mateus found the nearly complete cranium and jaw of C. mukulu, along with 12 associated teeth and other fossilized parts of the reptile's body in Bentiaba, Angola in 2017. That area is on the coast of Angola that Jacobs has called a "museum in the ground," because so many fossils have been found in the rocks there.

Many of those fossils are currently on display at the Smithsonian's National Museum of Natural History. The museum's "Sea Monsters Unearthed" exhibit, co-produced with SMU, features large marine reptiles from the Cretaceous Period -- mosasaurs, turtles, and plesiosaurs.

Jacobs and Polcyn forged the Projecto PaleoAngola partnership with collaborators in Angola, Portugal, and the Netherlands to explore and excavate Angola's rich fossil history and began laying the groundwork for returning the fossils to the West African nation. Back in Dallas, Jacobs, Polcyn, and research associate Diana Vineyard went to work over a period of 13 years with a small army of SMU students to prepare the fossils excavated by Projecto PaleoAngola.

Like the Smithsonian exhibit, the discovery of the Cardiocorax mukulu remains were the result of that collaboration.

CT scan shows jaws and teeth of elasmosaurids didn't evolve much

Marx's computed tomography (CT) scan of the skull was designed to reveal parts of the skull that are otherwise difficult to see, such as the braincase. Only part of the skull was actually freed from the Angolan rock in which it was discovered because elasmosaurids skulls are so fragile. So the CT scan was taken largely through the rock that preserved the specimen.

However, "the good resolution of the resulting CT images allowed me to discriminate between the bone, the rock matrix, and the plaster jacket the skull was protected in," Marx said. "Thus, I could build a 3D model of the skull and be able to study the fragile parts of it, such as the braincase and palate, without touching it."

The team's conclusions about the cranial anatomy of C. mukulu were drawn from comparisons to the skull of Libonectes morgani, a much older elasmosaurid housed at SMU.

"The skull of L. morgani at SMU is so complete that the sutures between different bones can clearly be delineated," he said. "The skull of Libonectes morgani worked as a guide for me when making the skull model of Cardiocorax mukulu. This made the process of building the model much faster."

Marx and the PaleoAngola team also compared the 3D imaging to the skulls of Styxosaurus snowii and Thalassomedon haningtoni -- all elasmosaurids from different time periods.

The similarity between the jaws, teeth and other skull anatomy of C. mukulu and its predecessors was a surprising discovery, Marx said.

Read more at Science Daily

Not just lizards: Alligators can regrow their tails too, new study reveals

 

American alligator

An interdisciplinary team of scientists using advanced imaging technology have answered the question of whether alligators share any of the same regenerative capabilities as much smaller reptiles. Many kinds of small reptiles, such as lizards, are known to regrow their tails. However, with a potential body length of 14 feet, little was known about whether alligators could possibly regrow their massive tails.

A team of researchers from Arizona State University and the Louisiana Department of Wildlife and Fisheries have uncovered that young alligators have the ability to regrow their tails up to three-quarters of a foot -- about 18% of their total body length. They speculate that regrowing their tails gives the alligators a functional advantage in their murky aquatic habitats.

The team combined advanced imaging techniques with demonstrated methods of studying anatomy and tissue organization to examine the structure of these regrown tails. They found that these new tails were complex structures, with a central skeleton composed of cartilage surrounded by connective tissue that was interlaced with blood vessels and nerves. Their findings are published in the journal Scientific Reports.

"What makes the alligator interesting, apart from its size, is that the regrown tail exhibits signs of both regeneration and wound healing within the same structure," said Cindy Xu, a recent PhD graduate from ASU's School of Life Sciences molecular and cellular biology program and lead author of the paper.

"Regrowth of cartilage, blood vessels, nerves and scales were consistent with previous studies of lizard tail regeneration from our lab and others," she said. "However, we were surprised to discover scar-like connective tissue in place of skeletal muscle in the regrown alligator tail. Future comparative studies will be important to understand why regenerative capacity is variable among different reptile and animal groups."

"The spectrum of regenerative ability across species is fascinating, clearly there is a high cost to producing new muscle," said Jeanne Wilson-Rawls, co-senior author and associate professor with ASU's School of Life Sciences.

Alligators, lizards and humans all belong to a group of animals with backbones called amniotes. In addition to previous studies about the ability of lizards to regrow their tails, the discovery of such large and complex new tails in alligators provides considerable new information about regenerative process in the larger animal classification of amniotes.

This also leads to new questions about the history of these capabilities, and the possibilities for the future.

"The ancestors of alligators and dinosaurs and birds split off around 250 million years ago," said co-senior author Kenro Kusumi, professor and director of ASU's School of Life Sciences and associate dean in The College of Liberal Arts and Sciences.

"Our finding that alligators have retained the cellular machinery to regrow complex tails while birds have lost that ability raises the question of when during evolution this ability was lost. Are there fossils out there of dinosaurs, whose lineage led to modern birds, with regrown tails? We haven't found any evidence of that so far in the published literature."

The researchers hope their findings will help lead to discoveries of new therapeutic approaches to repairing injuries and treating diseases such as arthritis.

"If we understand how different animals are able to repair and regenerate tissues, this knowledge can then be leveraged to develop medical therapies," said Rebecca Fisher, co-author and professor with the University of Arizona College of Medicine-Phoenix and ASU's School of Life Sciences.

Read more at Science Daily