Some ancient crocodile species were herbivores

Based on the detailed analysis of tooth remains, researchers have discovered that some ancient crocodilians were herbivores. The study findings suggest that the carnivorous preferences of crocodiles were replaced with plants at least three times among the distant relatives of modern crocodilians.

“The most interesting thing we discovered was how frequently it seems extinct crocodyliforms ate plants,” said study author Keegan Melstrom of the University of Utah. “Complex teeth, which we infer to indicate herbivory, appear in the extinct relatives of crocodiles at least three times and maybe as many as six in our dataset alone.”

As semiaquatic generalist carnivores, all modern-day crocodilians have relatively simple and consistent teeth. The extinct species examined for the study clearly showed a different pattern, including many specializations that are not seen today. One feature that was found among the fossils was the primitive characteristic of heterodonty, or teeth of different shapes and sizes. 

“Carnivores possess simple teeth whereas herbivores have much more complex teeth,” explained Melstrom. “Omnivores, organisms that eat both plant and animal material, fall somewhere in between. Part of my earlier research showed that this pattern holds in living reptiles that have teeth, such as crocodilians and lizards. So these results told us that the basic pattern between diet and teeth is found in both mammals and reptiles, despite very different tooth shapes, and is applicable to extinct reptiles.”

The researchers compared the tooth complexity of prehistoric crocodyliforms with those of living animals to reconstruct their diets. Overall, they measured 146 erupted teeth from 16 different taxa of extinct crocodyliforms.

Crocodyliform life reconstructions. Image Credit: Jorge Gonzalez

The study revealed that shortly after the end-Triassic mass extinction, plant-eating crocodilians emerged and persisted until the end-Cretaceous mass extinction. There was also evidence to suggest that a preference for plants appeared independently at least three times in Mesozoic crocodilians.

“Our work demonstrates that extinct crocodyliforms had an incredibly varied diet,” said Melstrom. “Some were similar to living crocodilians and were primarily carnivorous, others were omnivores, and still others likely specialized in plants. The herbivores lived on different continents at different times, some alongside mammals and mammal relatives, and others did not. This suggests that an herbivorous crocodyliform was successful in a variety of environments!”

The study is published in the journal Current Biology.

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By Chrissy Sexton, Earth.com Staff Writer

Main Image Credit: Shutterstock/Ondrej Prosicky