'Palm-sized predator' with outsized teeth rewrites lizard origins

Scientists used the European Synchrotron Radiation Facility to X-ray the tiny fossil and reveal high-resolution details.

By Jerusalem Post Staff, September 12, 2025

https://www.jpost.com/archaeology/article-867252

An illustration of the newly discovered lizard ancestor. (photo credit: Bob Nicholls)

Scientists announced on Wednesday that they identified the oldest known ancestor of today’s lizards: a tiny reptile from southwest England that was about 242 million years old and lived during the Middle Triassic, shortly before the rise of the dinosaurs. The fossil, the oldest known member of Lepidosauria, was found in a rock block collected in 2015 on a beach in Devon, and the study appeared in the journal Nature.

The animal was small enough to fit in a human palm, had humans existed at the time. Its skull measures about 1.5 centimeters wide and was embedded in a large rock, which made study difficult. Researchers used imaging to resolve the anatomy of the skull and skeleton and to test where the animal fit in the early evolution of lizards, snakes, and the tuatara.

To address the challenges of size and preservation, the team used the European Synchrotron Radiation Facility to X-ray the fossil and produce high-resolution images. The facility generated X-rays far brighter than medical machines. “The Synchrotron allowed the scientists to zoom in on large objects and obtain very high-resolution images,” said Vincent Fernandez, a paleontologist at the facility in France, according to a report by the Philippine Star.

The fossil showed a connecting bone between the cheek and jaw, a feature shared today only by the tuatara of New Zealand. Researchers said this bone likely enabled the animal to crack hard insect shells. They also reported that modern lizards and snakes have a partially hinged skull and many teeth on the roof of the mouth, features absent in the fossil.

The animal’s teeth were relatively large compared to its closest relatives and were suited to piercing and shearing the hard cuticles of insects such as cockroaches. The combination of a small skull, reinforced cheek-jaw connection, and oversized teeth indicated a diet focused on hard-bodied insects.

The team named the animal Agriodontosaurus helsbypetrae, after the Helsby Sandstone Formation where it was found, placing it within the Middle Triassic rock sequence of the region. The fossil extended the record of Lepidosauria, the lineage that gave rise to modern lizards, snakes, and the tuatara.

“The new animal was unlike anything yet discovered and made us all think again about the evolution of the lizard, snakes and the tuatara,” said Dan Marke of the University of Bristol.

The preparation of this article relied on a news-analysis system.