Researchers at the Smithsonian Institution have discovered an extinct reptile species that lived among dinosaurs in Jurassic North America, 150 million years ago. The species is a lizard-like reptile that belongs to the same ancient lineage as New Zealand's living tuatara. A team of scientists, including University College London and Natural History Museum, London scientific associate Marc Jones, the National Museum of Natural History's curator of Dinosauria Matthew Carrano and research associate David DeMar Jr, describe the new species Opisthiamimus gregori in a paper published September 15 in the Journal of Systematic Palaeontology.
All About Opisthiamimus gregori
Opisthiamimus gregori once inhabited Jurassic North America about 150 million years ago alongside dinosaurs like Stegosaurus and Allosaurus.
When the prehistoric reptile was alive, it would have been about 16 centimetres in length, from nose to tail. Also, 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 diminutive (unusually small) size, and a rigid skull, the researchers believe that it likely ate insects. In a statement released by Smithsonian Institution, DeMar said that prey with harder shells such as beetles or water bugs might have also been on the extinct reptile's menu.
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Where Was The Extinct Reptile Discovered?
The researchers had excavated some specimens, including an extraordinarily complete and well-preserved fossil skeleton, from a site centred around an Allosaurus best in northern Wyoming's Morrison Formation. The extinct reptile's fossils were among the specimens uncovered. It is not yet known why the animal's ancient order of reptiles declined from being diverse and numerous in the Jurassic to just New Zealand's tuatara surviving in the present day.
Are Tuataras And The Extinct Reptile Lizards?
In the statement released by Smithsonian Institution, Carrano said the tuatara represents an enormous evolutionary story that researchers are lucky enough to catch in what is likely its closing act . He said that even though the tuatara looks like a relatively simple lizard, it embodies an entire evolutionary epic going back more than 200 million years. The tuatara appears similar to a stout iguana. However, the tuatara and its newly discovered relative are not lizards at all, according to Carrano.
What Are Rhynchocephalians?
Tuatara and the extinct reptile are rhynchocephalians, an order that diverged from lizards at least 230 million years ago.
In the Jurassic period (200 million to 145 million years ago), rhynchocephalians were found nearly worldwide, and came in sizes large and small. They performed different ecological roles including aquatic fish hunting, and bulky plant munching. However, rhynchocephalians disappeared as lizards and snakes grew to be more common and more diverse reptiles across the globe.
Some Of Tuatara’s Odd Features
According to the study, the evolutionary rift between lizards and rhynchocephalians helps explain the tuatara's odd features 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 100-year-old life span, and a tolerance for colder climates.
Why Did Rhynchocephalians Disappear 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 find out why the tuatara is all that remains of the rhynchocephalians, and why lizards are now found across the globe.
Carrano explained these animals may have disappeared because of competition from lizards but also perhaps due to global shifts in climate 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 the bones from a block of stone. The block first caught museum fossil preparator Pete Kroehler's eye back in 2010.
Carrano said that Pete is one of those people who has a kind of X-ray vision for this sort of thing. Pete noticed two tiny specks of bone on the side of the block, and marked it to be brought back with no real idea what was in it, Carrano stated.
"As it turns out, he hit the jackpot," Carrano said.
Extinct Reptile’s Fossil Is Almost Entirely 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 because their frail bones were often destroyed either before they fossilised or as they emerged from an eroding rock formation in the present day, Carrano said.
This is the reason why rhynchocephalians are known to palaeontologists only from their jaws and teeth.
Scanning Of The Fossils, 3D Representation Of The Specimen
Kroehler, Gregor, and others feed as much of the tiny fossil from the rock as was practical, given its fragility. After this, the team, led by DeMar, started scanning the fossil with high-resolution computerised 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 possibly could about the fossil, the team used three separate CT scanning facilities. One of them was housed at the National Museum of Natural History.
The researchers digitally rendered the fossil's bones with accuracy smaller than a millimetre. Then, DeMar started reassembling the digitised bones of the skull, some of which were crushed, missing, or out of place, using software. Eventually, the team created a nearly complete 3D reconstruction. The researchers now have an unprecedented look at the Jurassic-age reptile's head, thanks to the reconstructed 3D skull.
The authors note that the new species looks a bit like a miniaturised version of its only surviving relative, the tuatara, which is about five times longer.