REPTILE THAT LIVED AMONG THE DINOSAURS DISCOVERED
This lizard-like animal belongs to the same ancient lineage as New Zealand’s living tuatara
The well-preserved fossil of an extinct species of lizard-like reptile has been discovered, shedding light on the evolution of the tuatara – the last living member of this once-diverse group of reptiles.
The fossil was discovered by a team of scientists from the National Museum of Natural History in Washington DC, University College London and the Natural History Museum. They found the new species at a site in Wyoming’s Morrison Formation and have named it Opisthiamimus gregori. It inhabited Jurassic North America around 150 million years ago, and lived among dinosaurs.
The reptile would have been about 15 centimetres long from nose to tail, and likely survived on a diet of insects and other small invertebrates.
“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,” said Matthew Carrano, one of the authors of the study and the curator of dinosaurs at the National Museum of Natural History.
“Even though it looks like a relatively simple lizard, it embodies an entire evolutionary epic going back more than 200 million years.”
After the team had freed as much of the fossil from the rock as possible without damaging it, they scanned it with high-resolution computerised X-ray tomography to make a 3D representation of the fossil. They then used software to painstakingly make a nearly complete 3D reconstruction, recreating bones that were crushed or damaged. They even managed to make a clear version of the skull.
Further study of the specimens found in Wyoming could help reveal why this animal’s order of reptiles dwindled. The order, Rhynchocephalia, once contained a diverse array of species, but New Zealand’s tuataras are the only surviving members.
Rhynchocephalians diverged from lizards roughly 230 million years ago. Rhynchocephalians were found around the world and came in a range of different shapes and sizes. However, for unknown reasons, they all but disappeared as lizard and snakes became more common.
The fossil has now been added to a museum collection where it will remain for additional study. Researchers hope to be able to one day understand why the tuatara is the last remaining rhynchocephalian.
“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.
“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.”