Triassic Lizard-Like Parareptile Had Unusual Dental Apparatus

Paleontologists have identified a new species of procolophonid reptile from the fossilized skull and jaw fragments found in southwest England.

The newly-discovered species, Threordatoth chasmatos, lived during the Late Triassic epoch, roughly 220-210 million years ago.

The ancient creature is a member of Leptopleuroninae, a subfamily of extinct lizard-like parareptiles within the clade Procolophonidae.

“Procolophonids were small parareptiles that appeared in the Late Permian, persisted through the end-Permian extinction event, and diversified across the supercontinent Pangea during the Triassic as a notable element of the post-extinction fauna,” said University of Birmingham paleontologist Luke Meade and his colleagues.

“Procolophonid diversity declined into the Late Triassic and is represented only by the late-diverging clade Leptopleuroninae, known from a small number of occurrences from Brazil, North America, Scotland, England and possibly Wales.”

“Leptopleuronine procolophonids typically have a reduced number of transversely expanded and bicuspid maxillary teeth and are often characterized by cranial ornamentation, including enlarged spines on the quadratojugal.”

“Leptopleuronines appear well-adapted to diets of high-fiber herbivory/omnivory or insectivory and the group may represent the latest surviving clade of Parareptilia.”

The fossilized remains of Threordatoth chasmatos were found in Cromhall Quarry in south Gloucestershire, southwest England.

“This small reptile’s teeth and jaw show features we’ve never seen before in its group,” said Dr. Meade, lead author of a study published in the journal Papers in Palaeontology.

“It likely fed in a way that distinguished it from its closest relatives, which opens up new questions about how these animals were interacting with their environment during the Late Triassic period.”

The reptile’s upper jaw features tricuspid teeth — each with three distinct points — while the lower jaw bears compressed monocuspid teeth with an unusual edentulous (toothless) tip.

These adaptations may have facilitated a distinct method of food processing.

“Inferring the interplay between the upper and lower teeth is fascinating, there are several aspects of the tooth shape that resemble those of mammals,” said Dr. Marc Jones, fossil reptiles curator at the Natural History Museum, London.

“The lower jaws were not fused at the chin, instead the connection was held with soft-tissue and likely flexible.”

“This flexibility might have allowed the lower jaws to meet in a way that would help chewing food.”

“This feature isn’t seen in closely related species and might indicate a specialized diet or feeding strategy.”

“The Late Triassic was a time of dramatic environmental change, as Pangea began to break apart.”

“The peculiar dental adaptations of Threordatoth chasmatos suggest it may have been exploiting a unique ecological niche in a changing climate, feeding on plants, insects, or other small prey that required specialized oral food processing.”

“Threordatoth chasmatos lived at a time when the solar irradiance was significantly lower than today but atmospheric carbon dioxide was significantly greater,” Dr. Jones said.

“Overall, it was hotter, average global sea level was higher, and there were extreme rainfall events.”

“Therefore, Threordatoth chasmatos and the community in which it lived could potentially provide perspectives for todays’ threatened ecosystems and the planetary emergency we face.”

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Luke E. Meade et al. 2024. A new procolophonid with complex dentition from the Late Triassic of southwest England. Papers in Palaeontology 10 (6): e1605; doi: 10.1002/spp2.1605