Photo worth seeing: Prehistoric lizards allow deep insight

© Jorge Herrera Flores/ University of Bristol

This fossil of an early scaled reptile reveals something about the anatomy of prehistoric lizards – and thus also about the beginnings of their evolutionary development.

It was previously agreed that most members of the squamates – the largest order of reptiles, which includes lizards and snakes – evolved at the end of the Mesozoic, before the dinosaurs became extinct. Because a lot of fossils of the so-called scaled reptiles come from the Cretaceous period, an era 145 to 66 million years ago, in which many new species generally arose due to the appearance of flowering plants.

In fact, there are few squamate fossils that date back to the Jurassic period, dating back as far as 200 million years. This raises the question of whether scaled reptiles were really few and far between at the time, or whether this is just due to poor preservation of fossils from that period. To answer this question, Arnau Bolet from the University of Barcelona and his colleagues analyzed the known fossils of early scaled reptiles and their characteristics in more detail.

Among the newly examined fossils is this prehistoric lizard, which is around 150 million years old. Their petrified relics were discovered as early as 1938 in the Solnhofen limestone near the town of Eichstätt in southern Germany – the same formation that had brought the famous Archeopteryx to light. The fossil of the gecko-like Eichstaettisaurus schroederi is believed to be one of the oldest and most complete relics of an early squamate.

The fossil analyzes by Bolet and his team now suggest that there could have been significantly more scaled reptiles than commonly assumed. “Although scaled reptile fossils from the Jurassic period are rare, reconstructed family trees show that all of their major specializations developed around this time,” explains senior author Michael Benton of the University of Bristol in the UK.

Above all, the diverse anatomy of the fossils has led to this assumption: they not only show original morphology, but already distinct features that can be assigned to groups that still exist today. “This means that the various adaptations of geckos, iguanas, worm lizards and snakes can be recognized about 50 million years earlier than previously thought,” reports Benton.

In the future, this knowledge could help to better understand the development of the unusually large diversity of this reptile order with more than 10,000 species.

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