Researchers have discovered an extinct prehistoric reptile that lived among the dinosaurs

Newswise — Smithsonian researchers have discovered a new extinct species of lizard-like reptile that belongs to the same ancient lineage as the living tuatara in New Zealand. A team of scientists, including National Museum of Natural HistoryDinosaur amine Matthew Carano and partner in research David DeMar Son. Beside University College London And the Natural History Museum, London Mark Jones, Scientific Fellow, describes the new species Let’s pray to Gregorywhich once inhabited Jurassic North America about 150 million years ago along with dinosaurs such as stegosaurus And the Allosaurusin a paper published today in Journal of Systematic Paleontology. In life, this prehistoric reptile was about 16 cm (about 6 inches) long from nose to tail – and would have curled up in the palm of an adult human – and likely survived on a diet of insects and other invertebrates.

“What’s important about the tuatara is that it represents this massive evolutionary story that we are lucky enough to capture in what is likely to be its closing event,” said Carano. “Although it looks like a relatively simple lizard, it exemplifies a whole evolutionary saga going back more than 200 million years.”

This find comes from a few specimens including a very complete and well-preserved fossil skeleton excavated from a site centered around Allosaurus Live in the Morrison Formation of northern Wyoming. Further study of the discovery could help reveal why the ancient order of reptiles of this animal disappeared from being diverse and numerous in the Jurassic to the surviving New Zealand tuatara today.

The tuatara look somewhat like a particularly powerful iguana, but the tuatara and its newly discovered relatives aren’t actually lizards at all. They’re actually rhynchocephalians, Carano said, something that differed from lizards at least 230 million years ago.

At the height of the Jurassic period, rhynchocephalians were found almost all over the world, and they came in large and small sizes, occupying ecological roles ranging from aquatic fishermen to huge plant cutters. But for reasons that are still not fully understood, both rhynchocephalians disappeared as lizards and snakes grew to become the most common and most diverse reptiles around the world.

This evolutionary gulf between lizards and rhynchocephalians helps explain tuatara’s peculiar features such as teeth fused into the jawbone, a unique chewing motion that slides the lower jaw back and forth like a saw blade, a lifespan of over 100 years and endurance of cold climates.

next Hey GregoryIn the official description, Carano said the fossil has been added to the museum’s collections where it will remain available for future study and may one day help researchers figure out why the tuatara are all that’s left of the rhynchocephalians, while lizards are now found all over the world. Globe.

“These animals may have disappeared partly because of competition from lizards but perhaps also because of global changes in climate and habitat change,” Carano said. “It’s amazing when you have the dominance of one group giving way to another over evolution time, and we still need more evidence to explain exactly what happened, but fossils like this are how we’re going to put them together.”

The researchers named the new species after museum volunteer Joseph Gregor, who spent hundreds of hours scraping and meticulously carving bones from a block of stone that first caught the museum’s excavator. Kroehler’s housein 2010.

“Pete is one of those people who has some kind of X-ray vision for this kind of thing,” Carano said. “He noticed two small pieces of bone on the side of this block and marked it to be turned back without any real idea of ​​what was inside. And as it turned out, he hit the jackpot.”

The fossil is almost completely complete, except for the tail and parts of the hind legs. Such a complete skeleton is rare for small prehistoric creatures like this because their weak bones were often destroyed either before they were petrified or as they emerged from an eroded rock formation today, Carano said. As a result, paleontologists mostly know about paleontologists from small fragments of their jaw and teeth.

After Kroehler, Gregor, and others freed as much of the small fossil from the rock as was practical due to its brittleness, the team led by DeMar set out to survey the fossil using high-resolution computerized tomography (CT), a method that uses multiple X-ray images from different angles to create A three-dimensional representation of the sample. The team used three separate CT scanning facilities, including one at the National Museum of Natural History, to capture everything they could about the fossil.

Once the fossil bones were digitally displayed at a resolution of less than a millimeter, DeMar proceeded to reassemble the digitized skull bones, some of which had been crushed, misplaced or lost on one side, using software to create a nearly complete 3D image in the final reconstruction. The now reconstructed 3D skull provides researchers with an unprecedented look at the head of this Jurassic reptile.

Given OpisthiamimusWith its small size and the shape of its teeth and a hard skull, Demar said it likely ate insects, adding that prey with tougher shells such as beetles or water bugs may also have been on the list. In general, the new species looks somewhat like a miniature version of its only surviving relative (the tuatara is about five times longer).

“Such a complete specimen has tremendous potential to make comparisons with fossils collected in the future and to identify or reclassify specimens that are already in a museum drawer somewhere,” Demar said. “With the 3D models that we have, at some point we can also do studies that use software to look at the mechanics of this creature’s decoding.”

Funding and support for this research was provided by the Smithsonian Institution and the Australian Research Council.

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