A team of researchers have discovered a new extinct species of lizard-like reptile that lived among dinosaurs. Opisthiamimus gregori lived in North America during the Jurassic period about 150 million years ago, during the same time as dinosaurs Stegosaurus and Allosaurus. The reptile belongs to the same lineage as the tuatara, which is found in New Zealand.
The discovery was made using a few specimens and a well-preserved fossil skeleton excavated in Wyoming, in the United States. The researchers plan to study why an entire ancient order of reptiles went all but extinct, only leaving behind the tuatara. The research is documented in a paper published in the Journal of Systematic Palaeontology.
“What’s important about the tuatara is that it represents this enormous evolutionary story that we are lucky enough to catch in what is likely its closing act. Even though it looks like a relatively simple lizard, it embodies an entire evolutionary epic going back more than 200 million years,” said Matthew Carrano, who was part of the research team, in a Smithsonian National Museum of Natural History press statement.
O.Gregori would have looked like an iguana with some heft but it and its relative, the tuatara, are not lizards at all. They both belong to the Rhynchocephalia order, which diverged from lizards at least 230 million years ago, according to Carano.
During their heyday in the Jurassic period, rhynchocephalians proliferated nearly worldwide and came in many different sizes. They filled many ecological niches that ranged from aquatic predators to bulky herbivores. But for some reason, they all but disappeared as lizards and snakes became the most diverse reptiles around the world.
The tuatara has some odd features that separate it from other reptiles like snakes and lizards, like teeth fused to the jaw bone and the fact that they can live up to a hundred years. These are explained by the evolutionary gap between them and other reptiles.
“These animals may have disappeared partly because of competition from lizards but perhaps also due to global shifts in climate and changing habitats. It’s 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,” said Carrano.
The fossil of the newly-discovered reptile is almost complete, apart from its tail and parts of its hind legs. According to Carano, such a complete skeleton is rare for small prehistoric creatures since their relatively fragile bones get destroyed either before or after they get fossilised.