Affichage des articles dont le libellé est Reptiles. Afficher tous les articles
Affichage des articles dont le libellé est Reptiles. Afficher tous les articles
Desmatosuchus
Before ankylosaurs invented the "tank" body plan, another group had already perfected it. Meet Desmatosuchus, the Triassic walking fortress.
This wasn't a dinosaur. It was an aetosaur—a heavily armored cousin of crocodiles and dinosaurs. In the river valleys of what is now Texas, over 220 million years ago, Desmatosuchus plodded along as a peaceful plant-eater. But "peaceful" didn't mean defenseless.
Its entire body, from neck to tail, was encased in interlocking bony plates (osteoderms). But its masterpiece was a pair of long, curved, spearlike spikes jutting from its shoulders, each as formidable as a bull's horns. This was a creature built to say, "Go ahead, try it," to any predator daring enough to attack.
Desmatosuchus represents the pinnacle of defensive evolution in its time. In a world of new and hungry predators, sometimes the best strategy isn't to outrun them, but to become literally too painful to eat.
Before dinosaurs ruled, the Triassic period was a laboratory of evolutionary experiments. One of its most successful—and intimidating—creations was a walking, grazing fortress named Desmatosuchus.
Imagine a 16-foot-long, heavily built herbivore, plodding through the river valleys of what is now Texas. Its entire back was covered in interlocking bony plates (osteoderms), forming a formidable suit of armor. But its pièce de résistance was a pair of long, curved spikes jutting from its shoulders, each as formidable as a bull's horns.
This wasn't a dinosaur, but an aetosaur—a heavily armored cousin of crocodiles and dinosaurs. In a world teeming with early crocodile-relatives and sharp-toothed predators, Desmatosuchus was built to survive. It likely used its pig-like snout to root for tubers and plants, while its intimidating shoulder spikes deterred even the most ambitious attackers.
Desmatosuchus is a masterpiece of defensive evolution. It proves that in the struggle for survival, sometimes the best strategy isn't to be the biggest or the fastest, but to be the one that's simply too much trouble to eat.
Phytosaurs (Gabriel N. U.)
Phytosaurs were a widespread and successful group of semi-aquatic, archosaurian reptiles that thrived during the Late Triassic period, approximately 235 to 201 million years ago. They were globally distributed, with fossils found on every modern continent, and were among the top predators in their ecosystems. Ranging in size from 2 to over 12 meters (6 to 40 feet) in length, they bore a remarkable, and classic, example of convergent evolution with much later animals.
Instead of being related to crocodiles, phytosaurs were a distinct lineage of archosaurs, a group that also includes crocodilians, pterosaurs, and dinosaurs. Their most iconic feature was an elongated, heavily armored skull, with nostrils positioned high on a bony crest in front of their eyes, not at the tip of the snout like a crocodile. This adaptation allowed them to breathe while almost completely submerged, much like a modern hippopotamus or crocodile. Their bodies were protected by rows of bony osteoderms (armor plates) embedded in the skin along their back and tail.
Phytosaurs were formidable carnivores, occupying the aquatic apex predator niche that crocodiles would later fill. Different species had different feeding strategies, reflected in their snout morphology: some, like Mystriosuchus, had long, slender, fish-catching snouts filled with numerous conical teeth, while others, like Nicrosaurus, had robust, deep snouts for grappling with larger terrestrial prey that came to the water's edge. They likely spent most of their time in rivers, lakes, and swamps, ambushing prey from beneath the water's surface. The extinction of the phytosaurs at the end of the Triassic period, likely due to widespread volcanic activity and climate change, opened the ecological door for the rise and diversification of the true crocodilians in the Jurassic, which would come to dominate the same semi-aquatic predatory roles for millions of years to come.
Hypuronector
Prepare to meet one of the strangest and most mysterious creatures from the prehistoric world: Hypuronector!
This unique animal from the Late Triassic period wasn't a dinosaur, but a type of reptile known as a drepanosaur. Its name, which means "deep-tailed swimmer," suggests it was an aquatic creature, perfectly at home in the water. However, its bizarre appearance has led to some fascinating scientific debate. As you can see in these incredible reconstructions, Hypuronector had a remarkably deep and flattened tail and an unusually tall dorsal "sail" along its back, which paleontologists believe may have been used for swimming.
But some researchers think its slender body and strange features made it a tree-dweller, using its long tail to grasp branches like a monkey. The theory is that its membranes may have even been used for gliding between trees, much like a flying squirrel. The artistic interpretations show this duality, with one image depicting it gliding through the branches and another showing its full, lizard-like form.
This amazing creature shows us just how bizarre and diverse prehistoric life could be. With only a few fossils to work from, its true lifestyle remains a fascinating puzzle for scientists.
Earliest Known Skin Fossil Shocks Paleontologists
A groundbreaking discovery reveals the oldest fossilized reptile skin, showing significant evolutionary features and offering a unique perspective on early terrestrial animal life. Preserved in an Oklahoma cave system, this finding sheds light on the development of skin adaptations in vertebrates.
Researchers have identified a 3D fragment of fossilized skin that is at least 21 million years older 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 was described recently in the journal Current Biology along with several other specimens that were collected from the Richards Spur limestone cave system in Oklahoma.
A Glimpse Into Ancient Life
“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.”
Uncovering the Details
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 that 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.”
Reptilian Features and Evolutionary Significance
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.”
Potential Ancestral Link and Preservation
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.
The skin fossil and other specimens were collected by lifelong paleontology enthusiasts Bill and Julie May at Richards Spur, a limestone cave system in Oklahoma that is an active quarry. The unique conditions at Richards Spur preserved many of the oldest examples of early terrestrial animals. The specimens are housed at the Royal Ontario Museum.
Premiers reptiles terrestres
C'est au Nouveau-Brunswick qu'on a découvert les plus anciennes empreintes de reptile du monde! Celles-ci sont très révélatrices car elles suggèrent que les reptiles auraient commencé à coloniser la terre trois millions d'années plus tôt que ce que l'on croyait jusqu'ici, c'est à dire il y a 318 millions d'années. Cliquez ici pour lire la nouvelle et voir une photo de la découverte. Extraordinaire de penser que de fragiles empreintes dans la boue puissent survivre aussi longtemps dans un état impeccable!
Pappochelys rosinae: l'ancêtre des tortues
It’s a primitive turtle, but it looks nothing like today’s dome-shelled reptiles. Resembling a broad-bodied, short-snouted lizard, the 240-million-year-old creature—dubbed Pappochelys rosinae—appears to be a missing link between prototurtles and their modern relatives, according to a new study. If so, the find could fill in a number of pieces about turtle evolution.
(...) About two dozen or so fossils of the creature have been recovered, all of them from 240-million-year-old rocks deposited as sediment on the floor of a shallow, 5-kilometer-long lake in what is now southern Germany.
(...) P. rosinae adults likely measured about 20 centimeters long, with half of that being a long, whiplike tail. (The species name is a combination of the Greek words for “grandfather turtle” and the person who helped clean rock from the fossils to prepare them for analysis.) Its peglike teeth suggest the animal fed on worms and other soft-bodied prey, Sues says.
(...) Unlike lizards, but much like the earliest known relative of turtles (Eunotosaurus, which lived in what is now South Africa about 20 million years earlier), Pappochelys’s ribs are broad, dense, and have a T-shaped cross section. In later, full-shelled species of turtles, those ribs are even wider and have fused with each other and certain bones in the shoulder girdle to form a carapace, or upper shell. But unlike the earlier Eunotosaurus, Pappochelys has gastralia, or belly ribs. These free-floating bones developed within the tissue of the underbelly, Sues says; in more evolved species of turtles, these gastralia broaden and fuse to form a plastron, or lower shell.
Because the fossils were originally entombed in lake floor sediments, the researchers suggest that Pappochelys spent a lot of its time in the water and around the lakeshore—a lifestyle similar to that of today’s marine iguanas, Sues says. So having broad, dense bones and gastralia would have acted like a diver’s weight belt, helping Pappochelys fight buoyancy and forage on the lake’s bottom. But these bones would also have had a beneficial side effect: They would have offered some degree of protection from predators, such as large amphibians or fish living in the lake, by deflecting or blunting their bites.
“In the water, predators can get you from all angles,” Sues notes. Over millions of years, evolution sculpted the bones to create the full set of body armor seen in modern-day turtles. The first full-shelled turtles show up in the fossil record about 205 million years ago.
Hypuronector (NTamura)
Hypuronector limnaios, a strange lizard like creature from the Late Triassic of New Jersey. Probably arboreal, even possibly a glider, as its very long limbs may have sported a patagium.
Revueltosaurus
Revueltosaurus est un des rares pseudosuchiens du Trias supérieur à être herbivores. À cette époque ce rôle est souvent alloué aux aétosaures ou à d'autres animaux qui ne sont pas des pseudosuchiens (cynodontes et dicynodontes...).
Revueltosaurus ressemble beaucoup à un pseudosuchien carnivore mais quand on voit ses dents, on est sûr qu'il mangeait des plantes. Les dents sont en forme de feuilles dentelées un peu comme celles des iguanes.
Il vivait au Norien, une période relativement longue de la fin du Trias où la diversité animale est relativement importante. Il s'éteindra à la fin de cette période sûrement concurrencé par des herbivores plus spécialisés comme les aétosaures.
Wikipedia:
Revueltosaurus ("Revuelto lizard") is an extinct genus of suchian pseudosuchian[1] from Late Triassic (late Carnian to middle Norian stage) deposits of New Mexico, Arizona and North Carolina, United States. Many specimens, mostly teeth, have been assigned to Revueltosaurus over the years. Currently, three species are included in this genus, all of which were originally thought to represent monospecific genera of basal ornithischian dinosaurs. It was 1 meter (3.3 feet) long.
Woman on beach finds fossil from unknown animal likely older than dinosaurs
High school teacher Lisa St. Coeur Cormier was strolling with her dog near her home on Canada’s Prince Edward Island when something caught her eye.
She often finds sea glass when she’s walking Sammy, but this day she thought she spotted a branch or tree root poking out of the sand.
“I saw something about two feet long with a strange shape,” said Cormier, 36, who lives in Charlottetown. “When I looked closer, I realized there was a rib cage. And around that, there was a spine and a skull.”
Cormier, who used to be a middle school science teacher, immediately knew it was a fossil. But she never imagined how rare and old, or the excitement that would develop from her discovery that day, Aug. 22.
It turns out the fossil is probably about 300 million years old, possibly from a species that no longer exists, said John Calder, a geologist and paleontologist from Halifax, Nova Scotia. That’s before the Jurassic period, when dinosaurs roamed the earth about 200 million years ago.
“There aren’t very many specimens from this period, so it was an incredible find,” Calder said about the fossil.
A photo of the fossil Cormier found landed on his desk after she took pictures and her family began contacting experts about her discovery.
“Something like this comes along every 50 to 100 years,” said Calder, who wrote a book about the geology of Prince Edward Island. “I thought, ‘My goodness, it needs to be collected right away before more bits wash away.’ ”
His emotional support animal is an alligator. They sleep in the same bed.
Calder estimates that the fossil is from the end of the Carboniferous period and into the Permian period.
“It is likely a reptile or a close relative, but it could also be unknown,” he said.
The fossil had probably recently been exposed to the elements and was in danger of washing away in the tide, he said.
Calder put a plan together, packed up his gear and made a trip to Prince Edward Island on Aug. 26 to carefully dig up the fossil with a Parks Canada crew.
“I was really nervous about the tides and was so glad when they arrived,” Cormier said.
“To think that this fossil might have been here 60 to 100 million years before the arrival of dinosaurs was so exciting that I couldn’t sleep,” she added.
She understood the potential importance of her discovery.
“I kept thinking of all the times I’d taught my science students about fossils,” Cormier said. “And now, here I’d found a significant one.”
MacNeil said that, like Calder, she was anxious to get the fossil safely out of the bedrock and into the hands of expert paleontologists.
Grandmother and grandson visit 62 national parks on adventure of a lifetime
She said the fossilized skeleton Cormier found is an extraordinarily uncommon discovery on Prince Edward Island.
“I was really excited to think what this could mean for the island,” she said.
After Calder took a close look at the fossil, he and his excavation crew got to work. They were joined by Cormier and MacNeil; Cormier’s husband, Gabriel Cormier; and her father-in-law, Aubrey Cormier, as they delicately dug two feet down to bedrock to put a trench around the skeleton.
“We were racing against time to get it out before sunset,” Calder said. “It took a lot of digging and fine chiseling. Once you start doing that, you’re committed to retrieving it in a short window before the tide comes in.”
More than five hours later, everyone was relieved when the skeleton was gently lifted out in three pieces surrounded by rock, he said.
Parks Canada workers then drove the fossil 36 miles across the island to a makeshift paleontology repository in Greenwich, where it will be stored until it is moved again to a paleontology lab in Nova Scotia for a CT scan.
Calder said they want to see what is inside the rock and get a better idea of how to safely remove the fossil.
“It will be a painstaking challenge to keep everything together because the rock is so soft,” he said. “It is a mud stone as opposed to a sandstone.”
Once the fossil is scanned, it could be sent to the Smithsonian National Museum of Natural History in D.C. or the Canadian Museum of Nature in Ottawa, where experts will remove all of the rock surrounding the skeleton and begin studying the specimen, he said.
An old dog was left at a shelter to be put down. Instead she’s living her best life.
“It will probably take a year to figure out exactly what this is,” Calder said. “We’re not 100 percent sure that it’s a reptile.”
Calder said the fossilized creature was probably similar in appearance to a Gila monster.
“Ultimately, it will be up to the scientists who publish a paper [about it] to decide what it should be called,” he said.
Cormier said she is excited for that to happen. But first, she can’t wait to tell her students when classes start next week — she now teaches French and history — about what she stumbled upon.
“What are the odds that I would go out for a walk and come across this fossil at the precise moment that it was exposed and nothing was covering it?” she said. “I’m in awe.”
Arizonasaurus (Gabriel Ugueto)
Arizonasaurus, a species of ctenosauriscid archosaur from Middle Triassic North America.
It was about 3 m. long and had tall neural spines on its back vertebrae that would have supported either a sail or hump (that served as fat storage) on its back.
60 million years of climate change drove the evolution and diversity of reptiles
Just over 250 million years ago during the end of the Permian period and start of the Triassic, reptiles had one heck of a coming out party.
Their rates of evolution and diversity started exploding, leading to a dizzying variety of abilities, body plans, and traits, and helping to firmly establish both their extinct lineages and those that still exist today as one of the most successful and diverse animal groups the world has ever seen. For the longest time, this flourish was explained by their competition being wiped out by two of the biggest mass extinction events (around 261 and 252 million years ago) in the history of the planet.
A new Harvard-led study has rewritten that explanation by reconstructing how the bodies of ancient reptiles changed and by comparing it against millions of years of climate change.
Harvard paleontologist Stephanie Pierce's lab shows that the morphological evolution and diversification seen in early reptiles not only started years before these mass extinction events but instead were directly driven by what caused them in the first place—rising global temperatures due to climate change.
"We are suggesting that we have two major factors at play—not just this open ecological opportunity that has always been thought by several scientists—but also something that nobody had previously come up with, which is that climate change actually directly triggered the adaptive response of reptiles to help build this vast array of new body plans and the explosion of groups that we see in the Triassic," said Tiago R. Simões, a postdoctoral fellow in the Pierce lab and lead author on the study.
"Basically, [rising global temperatures] triggered all these different morphological experiments—some that worked quite well and survived for millions of years up to this day, and some others that basically vanished a few million years later," Simões added.
In the paper, which published Friday in Science Advances, the researchers lay out the vast anatomical changes that took place in many reptile groups, including the forerunners of crocodiles and dinosaurs, in direct response to major climate shifts concentrated between 260 to 230 million years ago.
The study provides a close look at how a large group of organisms evolve because of climate change, which is especially pertinent today as temperatures continually rise. In fact, the rate of carbon dioxide released into the atmosphere today is about nine times what they were during the timeframe that culminated in the biggest climate change-driven mass extinction of all time 252 million years ago: the Permian-Triassic mass extinction.
"Major shifts in global temperature can have dramatic and varying impacts on biodiversity," said Stephanie E. Pierce, Thomas D. Cabot Associate Professor of Organismic and Evolutionary Biology and curator of vertebrate paleontology in the Museum of Comparative Zoology. "Here we show that rising temperatures during the Permian-Triassic led to the extinction of many animals, including many of the ancestors of mammals, but also sparked the explosive evolution of others, especially the reptiles that went on to dominate the Triassic period."
The study involved close to eight years of data collection and took a heavy dose of camerawork, CT scanning, and loads of passport stamps as Simões traveled to more than 20 countries and more than 50 different museums to take scans and snapshots of more than 1,000 reptilian fossils.
With all the information, the researchers created an expansive dataset that was analyzed with state-of-the-art statistical methods to produce a diagram called an evolutionary time tree. Time trees reveal how early reptiles were related to each other, when their lineages first originated, and how fast they were evolving. They then combined it with global temperature data from millions of years ago.
Diversification of reptile body plans started about 30 million years before the Permian-Triassic extinction, making it clear these changes weren't triggered by the event as previously thought. The extinction events did help put them in gear though.
The dataset also showed that rises in global temperatures, which started at about 270 million years ago and lasted until at least 240 million years ago, were followed by rapid body changes in most reptile lineages. For instance, some of the larger cold-blooded animals evolved to become smaller so they could cool down easier; others evolved to life in water for that same effect. The latter group included some of the most bizarre forms of reptiles that would go on to become extinct such as a giant, long-necked marine reptile once thought to be the Loch Ness monster, a tiny chameleon-like creature with a bird-like skull and beak, and a gliding reptile resembling a gecko with wings. It also includes the ancestors of reptiles that still exist today like turtles and crocodiles.
Smaller reptiles, which gave rise to the first lizards and tuataras, went on a different path than their larger reptile brethren. Their evolutionary rates slowed down and stabilized in response to the rising temperatures. The researchers believe it was because the small-bodied reptiles were already better adapted to the rising heat since they can more easily release heat from their bodies compared to larger reptiles when temperatures got hot very quickly all-around Earth.
The researchers say they are planning to expand on this work investigating the impact of environmental catastrophes on evolution of organisms with abundant modern diversity, such as the major groups of lizards and snakes.
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