Ancient Crocodiles Flourished with the Dinosaurs: Diversity is King

Crocodiles may seem like living dinosaurs, but they are far different from the extinct creatures that thrived millions of years ago. In fact, crocodiles had to compete for resources in a dinosaur-dominated world. Now, scientists have uncovered the hidden past of crocodiles, revealing how they evolved and survived.

These days, most crocodiles live in freshwater habitats, feeding on mammals and fish. Yet their extinct relatives were far more diverse. There were some that could run around on land like dogs while others could live in the open ocean and fed like today's killer whales. In order to learn a little bit more about these ancient creatures, researchers examined how the jaws of ancient crocodiles evolved to allow them to survive in vastly different habitats while living alongside dinosaurs.

"The ancestors of today' crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts," said Tom Stubbs, the lead researcher, in a news release. "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. Their evolution and anatomical variation during the Mesozoic Era was exceptional. They evolved lifestyles and feeding ecologies unlike anything seen today."

The researchers examined differences in the shape and function of the lowers jaws in over 100 ancient crocodiles. They used a unique combination of numerical methods in order to do so as they analyzed what kinds of feeding methods these ancient crocodiles might have employed.

"We were curious how extinction events and adaptations to extreme environments during the Mesozoic--a period covering over 170 million years--impacted the feeding systems of ancient crocodiles and to do this we focused our efforts on the main food processing bone, the lower jaw," said Stephanie Pierce, one of the researchers, in a news release.

In the end, the researchers found that following the end-Triassic extinction, ancient crocodiles invaded the Jurassic seas and evolved jaws that were made for hydrodynamic efficiency. Their diversity peaked again in the Cretaceous, which is when ancient crocodiles evolved a great variety of lower jaw shapes in order to adapt to a range of feeding ecologies.

"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 Pierce.

The findings are published in the journal Proceedings of the Royal Society B.