Extinct Reptile That Roamed Earth When Dinosaurs Did Unearthed in U.S.

An extinct reptile that lived among the dinosaurs 150 million years ago has been unearthed in the badlands of Wyoming.

The tiny creature sheds light on New Zealand's Tuatara, the last living member of a group that has almost entirely been supplanted by lizards.

About 6 inches long from nose to tail, the "miniature version" would fit curled up in the palm of your hand. It snacked on insects - including beetles and primitive water bugs. Named Opisthiamimus gregori, its fossilized remains were entombed in rocks from a river floodplain dating back to the Late Jurassic.

Artist's depiction of Opisthiamimus gregori
An artist's depiction of the Opisthiamimus gregori. About 6 inches long from nose to tail, it would fit curled up in the palm of your hand. Its fossilized remains were entombed in rocks from a river floodplain dating back to the Late Jurassic in present-day Wyoming. SWNS/Zenger

Lead author Dr. Matthew Carrano, of the Smithsonian Institution in Washington D.C, said: "What's important about the Tuatara is it represents this enormous evolutionary story that we are lucky enough to catch in what is likely its closing act," adding that "even though it looks like a relatively simple lizard, it embodies an entire evolutionary epic going back more than 200 million years."

It is a mystery why Tuatara disappeared as lizards and snakes replaced them as the common reptiles across the globe.

Opisthiamimus has been added to the Smithsonian Museum's collections where it will remain available for future study. It may help researchers figure out why the tuatara is all that remains of the Rhynchocephalian, while lizards have spread around the planet.

"These animals may have disappeared partly because of competition from lizards but perhaps also due to global shifts in climate and changing habitats," Carrano said.

Fossilized remains of Opisthiamimus gregori
About 6 inches long from nose to tail, the fossilized remains of Opisthiamimus gregori were entombed in rocks from a river floodplain dating back to the Late Jurassic in present-day Wyoming. SWNS/Zenger

"It is fascinating when you have the dominance of one group giving way to another group over evolutionary time, and we still need more evidence to explain exactly what happened, but fossils like this one are how we will put it together."

The fossil is almost entirely complete, with the exception of the tail and parts of the hind legs. Its skeleton is rare for small prehistoric creatures. Their frail bones were often destroyed either before they fossilized or as they emerge from an eroding rock formation in the present day.

As a result, Rhynchocephalian are mostly known to paleontologists from small fragments of their jaws and teeth.

Tuatara called Tane at Zealandia wildlife park
German President Walter Steinmeier holds a Tuatara called Tane at Zealandia wildlife park on November 7, 2017, in Wellington, New Zealand. An extinct reptile that lived among the dinosaurs 150 million years ago has been unearthed in the badlands of Wyoming. The tiny creature sheds light on the Tuatara, the last living member of a group that has almost entirely been supplanted by lizards. Marty Melville-Pool/Getty Images via Zenger

Co-author David DeMar, a research associate, said: "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.

"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," said DeMar.

Opisthiamimus is described in the Journal of Systematic Palaeontology.

The researchers named the new species after museum volunteer Joseph Gregor.

Produced in association with SWNS Talker.

This story was provided to Newsweek by Zenger News.