Crocodiles are among the world's oldest surviving species, but how did their ancestors not only survive, but flourish among the dinosaurs? New research from Bristol University gives insight into the diversity and evolution of the ancient reptiles that evolved 235 million to 65 million years ago, Phys.org reports.
Though modern crocodiles live in freshwater habitats and eat fish and mammals, their prehistoric ancestors had a far more diverse array of feeding modes and morphologies. Some ran around like dogs on land, while others lived in the open oceans, efficient in capturing underwater prey in a similar manner to a modern day killer whale. The ancient crocodile represented a considerably diverse ecology, according to the researchers, yet their "macroevolutionary patterns remain unexplored."
"The ancestors of today's crocodiles have a fascinating history that is relatively unknown compared to their dinosaur counterparts," said Tom Stubbs, who led the research. "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."
To understand how these various types of crocodiles survived, the Bristol University research team used a unique combination of numerical methods to examine and analyze the morphology and biomechanics of 100 ancient crocodiles' lower jaws, their findings recently published in the journal Proceedings of the Royal Society B.
"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," Stephanie Pierce of The Royal Veterinary College told Phys.org.
As ancient crocodiles recovered from the end-Triassic extinction event, they began to take over the seas and subsequently evolved jaws "built primarily for hydrodynamic efficiency to capture agile prey, such as fish," though only a small section of prehistoric crocodiles were able to survive in such Jurassic marine environments. However, the variation of ancient crocodiles peaked once more during the Cretaceous period, evolving a variety of lower jaw shapes.
"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 exceptional variation of ancient crocodiles has never before been studied numerically, according to Phys.org, and no previous studies have incorporated such a wide range of crocodiles spanning such a long period of prehistoric time.
