The mysterious origin of lizards uncovered by discovery of new ancient fossil

Scene depicting the reconstruction of a lizard. (Image: Bob Nicholls)

A tiny fossil found on a Devon beach reveals secrets. Scientists from the University of Bristol studied the ancient discovery. The research was published today in Nature.

What Makes This Fossil Different From Modern Lizards?

The fossil belongs to the earliest members of Lepidosauria. This group includes lizards, snakes, and the tuatara from New Zealand. Today, they are the most successful land vertebrates. Together, they include over 12,000 species. Scientists wondered what made them so successful.

Researchers expected early lepidosaurs to show key lizard features. These include a hinged skull, an open lower temporal bar, and palatal teeth. Such features help modern lizards handle large or wriggling prey. The tuatara keeps a full lower temporal bar today.

But the new fossil defied all expectations. It lacked palatal teeth and a skull hinge. It did have an open temporal bar, though. Most strikingly, it featured unusually large triangular teeth. Scientists believe it used them to pierce insect exoskeletons.

Holotype specimen of Agriodontosaurus helsbypetrae, BRSUG 29950-14, alongside a close-up of the preserved skull. Scale bars represent 10mm and 5mm, respectively. (Image: Thitiwoot Sethapanichsakul)

How Did Scientists Study the Fossil’s Tiny Details?

Dr Dan Marke led the project as part of his MSc studies. The skull measured just 1.5 centimetres long. Regular scans provided some information, but details remained unclear.

Dr David Whiteside explained they used synchrotron X-ray technology. This high-resolution scanning revealed incredible fine details without damage. The European Synchrotron Radiation Facility in France and Diamond Light Source in the UK provided beamlines.

Three-dimensional model of A. helsbypetrae skull, reconstructed using synchrotron tomography. The silhouette shows the individual parts preserved in the holotype specimen. (Image: Dan Marke)

Michael Benton, co-supervisor, said the fossil fits in a palm. But after data clean-up, it showed amazing structural detail. The large teeth resembled those of today’s tuatara.

The fossil was named Agriodontosaurus helsbypetrae. It means "fierce-toothed lizard from Helsby rock". It was found in the Helsby Sandstone Formation.

What Does This Fossil Tell Us About Evolution?

The specimen dates back 242 million years, from the Middle Triassic. This was just before dinosaurs appeared. Lepidosaurs diversified over several stages after that. Early species hid under dinosaur feet in dense undergrowth.

Scientists believe the discovery shows the tuatara is not just a “living fossil”. It once belonged to a diverse ancient reptile order. The new fossil reshapes understanding of lizard evolution.

Dr Rob Coram, who found the fossil in 2015, shared excitement. He said the site has yielded fossils for 150 years. The find offers new insight into ancient reptile history.

This discovery raises new questions about evolutionary adaptations. Why did this ancient creature have huge teeth? How did it capture insects without a skull hinge? Scientists hope further studies will answer these mysteries.