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Researchers discover new species of extinct reptile related to New Zealand tuatara

Paleontologists unearthed fossil remains of a reptile that lived alongside Stegosaurus and Allosaurus dinosaurs in what is now Wyoming.

(CN) — Smithsonian researchers have discovered a new species of extinct reptile in the Jurassic Morrison Formation of Wyoming.

Researchers described the lizard-like species in a paper published Thursday in the Journal of Systematic Paleontology. They believe the new species, Opisthiamimus gregori, once inhabited Jurassic North America nearly 150 million years ago with the likes of Stegosaurus and Allosaurus dinosaurs.

At present, the only living animal of the order Rhynchocephalia is the tuatara, a small, iguana-like reptile endemic to New Zealand. However, researchers believe rhynchocephalians were once found worldwide with abundant, diverse populations that lived aquatically and terrestrially. The discovery of the new species strengthens this belief, as researchers spotted the fossil fragments in a cluster of rocks nearly 8,000 miles from where the tuatara lives now.

“It adds a species to this environment, which means that we've got at least four different species of these rhynchocephalians running around,” said Matthew Carrano, curator of Dinosauria at the National Museum of Natural History, of the Jurassic Morrison Formation in Wyoming, where dinosaur fossils are commonly found.

The new species’ skeleton is one of the first nearly complete fossil of rhynchocephalians in North America, whereas other species of the order are limited have been identified through fragments of teeth and jawbone. According to Carrano, the fossils are difficult to spot because they are small and don’t preserve well.

“We know frustratingly little about them,” Carrano said.

He added that the new species provides an evolutionary glimpse in how rhynchocephalians eventually gave way to staxon Squamata — the order of lizards and snakes — which diverged from rhynchocephalians around 230 million years ago.

“Only at the close of the Jurassic did Squamata begin to overshadow Rhynchocephalia as the predominant lepidosaur clade,” the study states. “The fossil record of Rhynchocephalia then diminishes, first in Laurasia and later in Gondwana, whereas that of squamates radically expanded.”

Carrano said that finding the fossils where there are lizards and rhynchocephalians together helps researchers understand what was going on.

“Are lizards competing with these things? Is there some big climate change thing that's happening over time? We don't really have an answer at the moment, but fossils like this, where we know the two animals are in the same place at the same time, are really helpful for that," Carrano said.

The evolutionary differences between lizards and rhynchocephalians, researchers believe, will also help explain strange features of the tuatara, like how its teeth are fused to its jawbone, its unique chewing motion of sliding its lower jaw like a saw blade, its tolerance to cold climates and ability to live to 100 years old.

From a cluster of rocks taken near an Allosaurus nest, research associate David DeMar Jr. managed to spot the animal’s tiny fossils and reconstruct its skeleton by digitally rendering fragments and piecing them together. Researchers estimate the prehistoric reptile would have been around 16 centimeters or six inches from nose to tail — small enough to fit in your hand.  

Because the reptile was so small, DeMar believes it most likely ate insects, but possibly also hard-shelled beetles or water bugs. According to a press release, the new species looks like a mini tuatara, which are about five times longer.

The new species is named after museum volunteer Joseph Gregor, who spent hundreds of hours excavating the fossils from a block stone found by fossil preparer Pete Kroehler in 2010.

“Pete is one of those people who has a kind of X-ray vision for this sort of thing,” Carrano said in the press release. “He noticed two tiny specks of bone on the side of this block and marked it to be brought back with no real idea what was in it. As it turns out, he hit the jackpot.”

Thanks to Gregor, the fossil is now nearly complete, and remains of Opisthiamimus gregori have been added to the museum’s collections for future study. Researchers hope this study inspires other paleontologists to revisit their specimens and look for tiny traces of rhynchocephalians.

“Such a complete specimen has huge potential for making comparisons with fossils collected in the future and for identifying or reclassifying specimens already sitting in a museum drawer somewhere,” DeMar said in the press release. “With the 3D models we have, at some point we could also do studies that use software to look at this critter’s jaw mechanics.”

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