Crocodiles are incredible creatures that are very successful predators, living in many different environments and rising to be apex predators in most areas.

People often comment on the fact that crocodiles have been around for a very long time, and they even get a reputation for not having evolved much in the past several million years.

While this may be true compared to many other species, it is not accurate to say that crocodiles never evolved, of course.

Researchers have found hundreds of fossilized bones throughout the Petrified Forest National Park in Arizona, many of which date back 216 million years. They have bones from at least 36 individuals, and likely many more.

What is interesting about these fossils is that they come from archosaurs, which are distant ancestors of crocodiles and other related animals.

When the bones are reconstructed, however, you don’t get an ancient but recognizable crocodile. Instead, you get an animal with much longer hindlimbs and shorter forelimbs, which means they were almost certainly bipedal. Estimates say that they were likely around 63.5 centimeters (25 inches) tall.

The findings from these fossils were published in the Journal of Vertebrate Paleontology. In a statement about the study, lead author and University of Washington graduate student Elliott Armour Smith said:

 “By analyzing the proportions of the limb skeletons of different animals, they determined its bipedal stance (standing on two feet) may have been the result of a differential growth pattern.”

So far, three shuvosaurid species have been described with features that appear to be like those of theropods. More research is needed to determine with certainty whether they are bipedal or not. Armour Smith went on to say:

“Although similar to the ornithomimid dinosaurs, these features would have evolved separately. And this similarity was probably due to the fact that croc-line and bird-line archosaurs evolved in the same ecosystems and converged upon similar ecological roles. Also, despite the fact that features like bipedalism, a toothless beak, hollow bones, and a large orbit are characteristic of ornithomimid theropod dinosaurs, shuvosaurids like Sonselasuchus show that these features evolved on the croc-line as well.”

The work that resulted in the study began back in 2014 and looks at more than 3000 fossils from the Sonselasuchus bonebed. There have been fossils from over 100 other species in this area as well, making it a very valuable resource for learning about not just dinosaurs but all animals that lived in the Southwestern USA millions of years ago.

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