From a distance, the pakasuchus, small terrestrial crocodiles that lived just over 100 million years ago in what is now West Africa, could have passed for peculiar felines. Experts believe that its slender limbs would allow it to move almost like a cat. In addition, they had fewer bony plates than other crocodilomorphs and their skull, also shorter and wider than that of most of their relatives, was also reminiscent of one of these felids. In fact, its dentition was similar to that of a mammal, and included large canines and teeth similar to molars and premolars.
Until now, most scientists thought that pakasuchus could have fed on small animals, such as insects or other invertebrates. However, a new study promoted by paleontologists Keegan Melstom and Randall Irmis, from the Utah Museum of Natural History, in the US, has revealed that this and many other extinct species related to current crocodiles and alligators probably ate plants.
Until now, most scientists thought that pakasuchus could have fed on small animals, such as insects or other invertebrates. However, a new study promoted by paleontologists Keegan Melstom and Randall Irmis, from the Utah Museum of Natural History, in the US, has revealed that this and many other extinct species related to current crocodiles and alligators probably ate plants.
As indicated in an essay published in the journal Current Biology , a careful analysis of the fossil teeth that have come down to us suggests that it was not an exceptional case; Throughout their evolutionary history, many crocodilomorphs followed a vegetarian diet at least three times. “Our work shows that complex dentitions, a characteristic of herbivores, appeared three to six times in these missing crocodile cousins,” says Melstrom.
Specialized teeth
All the species of the order of crocodiles that exist today have a similar anatomical configuration, suitable to follow a type of semi-aquatic life and a non-specialized carnivorous diet , as shown by their teeth, which are conical and relatively simple. However, the animals studied by Irmis and Melstrom had very different parts from each other, specially adapted to fulfill different functions, a variation that is present in mammals.
To determine what the extinct crocodilomorphs ingested, the researchers compared the morphology of 146 teeth from 16 species with the dentitions of their living relatives. Thus, they observed that those of the former were considerably richer from a structural point of view. Those that were exclusively herbivores appeared earlier in the group’s evolutionary history, the scientists say, shortly after the mass extinction in the late Triassic, about 250 million years ago. They survived until the end of the Cretaceous, when they disappeared along with the dinosaurs and many other species.
“The study of the ancient crocodilomorphs proves that they followed a much more varied diet than the current ones. Some were carnivores; others specialized in plants and there were even omnivores. Remains of those that were herbivores have been found on different continents and at different times, which indicates that they managed to spread through a wide variety of environments, ”says Melstrom in a note released by the University of Utah.
Reference: Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs . Keegan M. Melstrom and Randall B. Irmis. Current Biology (2019). DOI: https: //doi.org/10.1016/j.cub.2019.05.076
Images: pakasuchus (Smokeybjb via Wikimedia / GNU); pakasuchus dental models (Utah Museum of Natural History); (reconstructions of crocodilomorphs (Jorge Gonzalez / University of Utah).
