Paleontologists have discovered the complete skull and skeleton of the Triassic Lepidosaurus species – Agriodontosaurus Helsbypetrae – from the Hellsby Sandstone Formation in Devon, England.
Lepidosauria is the most species-rich group of terrestrial vertebrates.
This group comprises around 12,000 species of lizards and snakes, along with a single species of Rhynchocephalia, the Tuatara (Sphenodon Punctatus) from New Zealand.
Collectively known as Squamata, these lizards and snakes not only range in size but also possess highly mobile skulls that enable them to capture large prey effectively.
These vital features of their skulls are absent in tuatara, making the understanding of their common ancestor essential.
The scalypidosaurs thrived during the Triassic period, 252 to 201 million years ago, but incomplete fossils have led to some confusion. Many are general scale pidosauromorphs that lack squamous epithelium or Rhynchocephalians.
“It was always expected that the earliest scalypidosaurs would exhibit some lizard characteristics, such as partially hinged skulls, open lower bars, and numerous teeth on the palate.”
“All of these traits are found in modern lizards and snakes, enabling them to grasp large prey by extending their mouths and using palate teeth to seize smaller prey.”
“The lower bar acts akin to the cheekbone, situated between the cheek and the jaw hinge, and is absent in present-day lizards and snakes.”
“Snakes and many lizards possess all these traits while enhancing skull flexibility.”
“Only the tuatara features a completely low temporal bar, presenting an archaic appearance reminiscent of some early reptiles, coupled with some substantial palate teeth.”
The fossil remains of Agriodontosaurus Helsbypetrae were found in 2015 on a beach in Devon, UK.
The specimen is dated to 242 million years ago (middle Triassic epoch), just prior to the emergence of dinosaurs.
It is approximately 3 to 7 million years older than the oldest known Lepidosaurus, Wirtembergia, from the Erfurt Formation.
“The new fossils revealed characteristics we didn’t anticipate,” remarked Dan Mark, a paleontologist at the University of Bristol and the University of Edinburgh.
“There are no teeth on the palate nor indications of hinges. While there is an open bar on the side, it’s not just one of the three, but also features a grand, large tooth in comparison to its closest relatives.”
Agriodontosaurus Helsbypetrae measured about 10 cm in length and showcased a unique combination of traits.
“When you observe the fossil, the entire skeleton fits in the palm of your hand,” said Professor Michael Benton from the University of Bristol.
“However, thanks to student efforts in cleaning up and scanning the data, we are uncovering remarkable details.”
“This new species possesses relatively large triangular teeth, likely adapted for slicing through the tough exteriors of insect prey, similar to modern tuataras.”
“The discoveries challenge our understanding of the evolutionary pathways of lizards, snakes, and tuataras,” Mark concluded.
The study results were published today in the journal Nature.
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D. Marche et al. The origins of feeding adaptations in the oldest known Lepidosaurus. Nature Published online on September 10, 2025. doi:10.1038/s41586-025-09496-9
Source: www.sci.news
