American alligator/© Mark Kostich, Adobe Stock
From ScienceDaily:
Based on careful study of fossilized teeth, scientists have found that multiple ancient groups of crocodyliforms — the group including living and extinct relatives of crocodiles and alligators — were not the carnivores we know today. Evidence suggests that a veggie diet arose in the distant cousins of modern crocodylians at least three times.
We’ll leave it to a reader to draw a conclusion about that. 😉 But also note:
“The most interesting thing we discovered was how frequently it seems extinct crocodyliforms ate plants,” said Keegan Melstrom, a doctoral student at the University of Utah. “Our study indicates that complexly-shaped teeth, which we infer to indicate herbivory, appear in the extinct relatives of crocodiles at least three times and maybe as many as six.”
All living crocodylians possess a similar general body shape and ecology to match their lifestyle as semiaquatic generalist carnivores, which includes relatively simple, conical teeth. It was clear from the start of the study that extinct species showed a different pattern, including species with many specializations not seen today. One such specialization is a feature known as heterodonty: regionalized differences in tooth size or shape.
“Carnivores possess simple teeth whereas herbivores have much more complex teeth,” Melstrom explained. “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 crocodylians 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.” …
“Our work demonstrates that extinct crocodyliforms had an incredibly varied diet,” Melstrom said. “Some were similar to living crocodylians 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!” Paper. (access?) – Keegan M. Melstrom, Randall B. Irmis. Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs. Current Biology, 2019; DOI: 10.1016/j.cub.2019.05.076 More.
Note: Researchers: “It was clear from the start of the study that extinct species showed a different pattern, including species with many specializations not seen today. One such specialization is a feature known as heterodonty: regionalized differences in tooth size or shape.” Maybe the crocodiles had an arsenal of potential adaptations in their genes.
See also: Convergent evolution of crocodile and dolphin skull shapes
and
BBC: Crocodile Eyes “Fine-Tuned” For Lurking
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