New fossil rewrites our understanding of reptile evolution

An illustration depicting and ancient lizard hunting. PIC COURTESY/Bob Nicholls

A newly discovered fossil from Devon has provided rare insight into the appearance of the earliest members of the lizard lineage, and the findings include some unexpected traits, according to researchers at the University of Bristol.

Today, lizards, snakes, and the tuatara of New Zealand together form the Lepidosauria, the most diverse group of living land vertebrates, boasting more than 12,000 species - surpassing both birds and mammals. This remarkable success raises questions about which characteristics enabled their evolutionary advantage.

Paleontologists long assumed that the earliest lepidosaurs would already display key lizard-like features, including a partially flexible skull, an open lower temporal bar, and numerous teeth along the roof of the mouth (palate). In modern lizards and snakes, these adaptations allow the mouth to open extremely wide (skull hinge) to handle large prey, while palatal teeth help secure smaller, struggling animals.

The lower temporal bar, essentially a rod of bone forming the cheek, is missing in living lizards and snakes. Instead, they share additional adaptations that enhance skull flexibility. The tuatara is the exception: it retains a fully developed lower temporal bar, an ancient feature that gives it a more primitive appearance, along with large palatal teeth.

"The new fossil shows almost none of what we expected," said Dan Marke, who led the project. "It has no teeth on the palate, and no sign of any hinging. It does though, have the open temporal bar, so one out of three. Not only this, but it possesses some spectacularly large teeth compared to its closest relatives."

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