An extinct lizard like reptile that lived among dinosaurs recently discovered in Jurassic North America 150 million years ago

Researchers from the Smithsonian Institution have discovered an extinct species of reptile that lived among the dinosaurs of Jurassic North America 150 million years ago. The species is a lizard-like reptile that belongs to the same ancient lineage as the living New Zealand tuatara. A team of scientists, including University College London and the Natural History Museum, London science associate Marc Jones, National Museum of Natural History of Dinosauria curator Matthew Carrano and research associate David DeMar Jr, describe the new species Opisthiamimus gregori in an article published on September 15 in the Journal of Systematic Paleontology.

Everything on Opisthiamimus gregori

Opisthiamimus gregori once inhabited Jurassic North America around 150 million years ago alongside dinosaurs like Stegosaurus and Allosaurus.

When the prehistoric reptile was alive, it must have been about 16 centimeters long, from nose to tail. Additionally, the reptile likely survived on a diet of insects and other invertebrates. The reptile would fit curled up in the palm of an adult human hand.

Opisthiamimus gregori had a short (abnormally small) stature and a rigid skull, researchers believe it probably ate insects. In a statement released by the Smithsonian Institution, DeMar said prey with harder shells such as beetles or water bugs could also have been on the extinct reptile’s menu.

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Where was the extinct reptile discovered?

The researchers had excavated a few specimens, including an extraordinarily complete and well-preserved fossil skeleton, at a site centered around a better Allosaurus in the Morrison Formation of northern Wyoming. Fossils of the extinct reptile were among the specimens discovered. It is not yet known why the ancient reptile order of the animal went from being diverse and numerous in the Jurassic to only the New Zealand tuatara surviving today.

A Tuatara

are the tuataras and reptile lizards extinct?

In the statement released by the Smithsonian Institution, Carrano said the tuatara represents a huge evolutionary story that researchers have the chance to capture in what is likely its final act. He said that even though the tuatara looks like a relatively simple lizard, it embodies a whole evolutionary epic dating back more than 200 million years. The tuatara looks like a large iguana. However, the tuatara and its newly discovered relative aren’t lizards at all, according to Carrano.

What are Rhynchocephali?

Tuatara and the extinct reptile are rhynchocephali, an order that diverged from lizards at least 230 million years ago.

In the Jurassic period (200 million to 145 million years ago), rhynchocephali were found almost worldwide and came in large and small sizes. They performed different ecological roles, including hunting aquatic fish and nibbling on large plants. However, the rhynchocephali disappeared as lizards and snakes became more common and diverse reptiles across the world.

Some of Tuatara’s weird features

According to the study, the evolutionary gap between lizards and rhynchocephalans helps explain odd features of the tuatara such as teeth fused to the jaw bone. Tuataras have a unique chewing motion that slides the lower jaw back and forth like a saw blade, a lifespan of 100 years, and tolerance to colder climates.

Why have Rhynchocephali disappeared across the globe?

According to the statement, Carrano said the fossil has been added to the museum’s collections where it will remain available for future study. This may help researchers discover why the tuatara is all that remains of the rhynchocephali and why lizards are now found throughout the world.

Carrano explained that these animals may have disappeared due to competition from lizards, but also possibly due to global climate change and changing habitats.

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Why is the species named so?

The species is named after museum volunteer Joseph Gregor, who spent hundreds of hours meticulously scraping and chiseling bones from a block of stone. The block first caught the eye of museum fossil preparator Pete Kroehler in 2010.

Carrano said Pete is one of those people who has some kind of x-ray vision for this stuff. Pete noticed two tiny pieces of bone on the side of the block and marked it to be brought back without really knowing what was in it, Carrano said.

“Turns out he hit the jackpot,” Carrano said.

Extinct Reptile Fossil Nearly Complete

According to the study, the fossil is almost entirely complete except for the tail and parts of the hind legs. Such a complete skeleton is “rare” for small prehistoric creatures like this, as their fragile bones were often destroyed either before they fossilized or when they emerged from an eroded rock formation in modern times, Carrano said.

This is the reason why rhynchocephali are only known to paleontologists by their jaws and teeth.

Digitization of fossils, 3D representation of the specimen

Kroehler, Gregor and others feed on as much of the tiny fossil rock as possible, given its fragility. After that, the team, led by DeMar, began scanning the fossil with high-resolution computerized tomography (CT). This is a method that uses multiple x-ray images from different angles to create a 3D representation of a specimen.

In order to capture everything they could about the fossil, the team used three separate CT scan facilities. One of them was kept at the National Museum of Natural History.

The researchers digitally rendered the bones of the fossil with sub-millimetre precision. Next, DeMar began reassembling the scanned skull bones, some of which were crushed, missing or displaced, using software. Eventually, the team created an almost complete 3D reconstruction. Researchers now have an unprecedented look at the head of the Jurassic-era reptile, thanks to the reconstructed 3D skull.

The authors note that the new species looks a bit like a miniaturized version of its only surviving relative, the tuatara, which is about five times longer.

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