A remarkable reptile-like creature with an unusual jaw that lived more than 200 million years ago has been described as a new species.

evidence of the species Threordatoth chasmatoswas unearthed from a former quarry at Cromhall in south-west England – a site renowned for its abundant fossil remains dating to the Triassic period (roughly 252-201 million years ago). Over the past few decades, the site has yielded fossils reptiles, related dinosaurs and even one of the oldest known lizards.

Procolophonids are classified as parareptiles. These extinct creatures are similar to what we now call reptiles, but represent a distinct lineage that diverged from the common ancestor of today’s reptiles and birds.

For the latest study, palaeontologists examined a set of fossils from Cromhall held in the collections of various institutions. The fossils have never been studied in detail before.

Although the remains consisted of only incomplete jawbones, scientists soon realized that they represented a previously unknown species due to several distinctive features.

“These specimens had a lot of unusual features,” study author Marc Jones, curator of fossil reptiles at the Natural History Museum in London, said in a press release. “For example, the front part of the jaw is not fused together, and there is no obvious place where they join. Instead, we think the two halves of the jaw were probably connected by ligaments.”

“If this were the case, the jaw would be somewhat flexible. It could aid tooth-to-tooth contact during chewing and provide some shock-absorbing potential, preventing forces from being transferred between the two sides of the jaw.”

Previous research has shown that as procolophonids evolved during the Triassic, their number of teeth decreased – a possible sign that they were adapting to a more specialized lifestyle. Procolophon teeth are relatively complex and potentially allow animals to process a variety of foods, including plants and insects.

“As time goes on, we see that most procolophonids evolve double-pointed teeth and reduce the number of teeth,” said lead study author Luke Meade, associated with the University of Birmingham. “It is thought that this may have allowed these animals to eat a tougher diet, perhaps as they became more herbivorous.”

“Threordatoth pushed the tooth reduction trend further than any other procolophonid in the Late Triassic. He has only four teeth on each side of his jaw.”

The newly described species would likely look similar to modern horned lizards, with bony spikes on its head and potentially some bony armor on its body.

“I like to imagine them running around the sinkholes and crevices of southwest England in the late Triassic, looking for plants and bugs to eat while avoiding early dinosaur relatives,” Meade said.

Because procolophonid bones are typically quite small, in many cases they would have been damaged or destroyed before the fossilization process even began. This generally means that researchers must rely on teeth and jawbones, which are more often preserved, to learn about these animals. As a result, there is still a large gap in our knowledge of these prehistoric creatures.

“If we continue to investigate sites like Cromhall, we can hopefully answer some of our outstanding questions,” Jones said.

Link

Meade, LE, Butler, RJ, Jones, MEH and Fraser, NC (2024). A new procolophonid with complex dentition from the Late Triassic of south-west England. Papers in paleontology, 10(6). https://doi.org/10.1002/spp2.1605