A newly discovered fossil from Devon has provided rare insight into the appearance of the earliest members of the lizard lineage, revealing 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. This group boasts more than 12,000 species, surpassing both birds and mammals in diversity. Such remarkable evolutionary success raises questions about which characteristics enabled their advantage.

Paleontologists long assumed that the earliest lepidosaurs already exhibited 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, thanks to a specialized skull hinge, enabling them to handle large prey. Meanwhile, palatal teeth help secure smaller, struggling animals.

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

However, the new fossil shows almost none of what scientists expected, explained Dan Marke, who led the project. The fossil has no teeth on the palate and shows no sign of any hinging mechanism. It does, however, possess an open temporal bar—so one out of three expected features is present. Interestingly, it also has some spectacularly large teeth compared to its closest relatives.

This discovery challenges previous assumptions about early lepidosaur evolution and offers new directions for future research into the origins and adaptations of this successful reptile group.

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