The diets of early lizards and snakes may have been more varied and advanced than previously believed, according to new research looking at their prehistoric teeth.

Scientists originally thought that squamates – the collective term for the 10,000 species of lizards and snakes – only began getting a taste for a much wider variety of food sources after dinosaurs became extinct.

But a study led by the University of Bristol, published in Royal Society Open Science, suggests they may have already possessed the full spectrum of diet types 100 million years ago, including flesh-eating and plant-based, seen today.

A team looked at fossil teeth and jaws from the Cretaceous period, between 145-66 million years ago.

Lead author, Dr Jorge Herrera-Flores, said: “We don’t know for sure how diverse squamates were in the Cretaceous.

“But we do know they had already achieved the full modern-type diversity of feeding modes by 100 million years ago, in the middle of the Cretaceous.

“Before that, squamates had already existed for more than 100 million years, but they seemed to be mainly insect-eaters up to that point.”

Scientists analysed fossils of several extinct large marine reptiles, measuring their jaws and teeth, before allocating them to dietary classes by comparison with modern forms.

Insect eaters have long peg-like teeth, while those who preferred to chomp on plants have flat teeth.

Sharp, pointed teeth belong to predators, and snakes tend to have hooked teeth to grasp their prey.

“Studying teeth and jaws provides excellent insights into dietary and ecological variety,” said co-author Dr Tom Stubbs.

“Fossil teeth and jaws give us the best insight into squamate evolution in the past.

“It would be easy to read the fossil record wrongly because of incomplete preservation. However, more fossil finds could only increase the number of feeding modes we identify in the Cretaceous, not reduce them.”