My, what pretty teeth you have! Research published in the journal Proceedings of the Royal Society B shows for the first time that ancient crocodiles were able to survive in very different environments and survive the mass extinction that killed off the dinosaurs 65 million years ago. Their survival tool? A wide array of jaw structures.

“The ancestors of today’s crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts,” said Tom Stubbs, who lead the research at the University of Bristol. “They were very different creatures to the ones we are familiar with today, much more diverse and, as this research shows, their ability to adapt was quite remarkable.”

Most of today’s crocodiles live in freshwater, feeding on mammals and fish, but their prehistoric ancestors were way more diverse. Some ancient crocodiles could scamper along on land like dogs, and others could live in the open ocean and feed the same way orca whales do today. To learn more about these ancient reptiles, researchers examined the different jaw structures of ancient crocodiles, determining how the evolution allowed them to survive in all the different ecosystems while living alongside dinosaurs, major competitors for food and resources.

A team led by Dr. Emily Rayfield and Stubbs studied these jaw structures, with the help of Dr. Stephanie Pierce from The Royal Veterinary College and Dr. Phil Anderson from Duke University. The research team used a unique combination of numerical methods to examine variation in the shape and function of the lower jaws in more than 100 ancient crocodiles. Using these methods, they analyzed what kinds of feeding methods these ancient crocodiles might have used.

By evolving many different jaw types, the ancient crocodiles were able to avoid the mass extinction fate of the dinosaurs during the end of the Triassic period. The research team found that after the end-Triassic extinction, ancient crocodiles took to the seas, flourishing during the Jurassic period after evolving jaws that were made for hydrodynamic efficiency and enabled them to adapt to many different types of ecologies. Their diversity peaked again in the Cretaceous period, though this time it was not due to another evolution of the jaw, but rather adaptions in other anatomical areas such as the development of armadillo-like armor.

“Our results show that the ability to exploit a variety of different food resources and habitats by evolving many different jaw shapes, was crucial to recovering from the end-Triassic extinction and most likely contributed to the success of Mesozoic crocodiles living in the shadow of the dinosaurs,” said Dr. Stephanie Pierce, from The Royal Veterinary College.