A popular reaction upon seeing an alligator or crocodile is to picture the beasts as living relics from an ancient time. Not only is that true, a new discovery by NC State researchers reveals that before dinosaurs reached North America, the top land predator was the affectionately-named “Carolina Butcher” – a nine foot long, bipedal species of crocodile.
Properly known as Carnufex carolinensis, the was identified based on skull, spine and forelimb fragments found at the Pekin Formation in Chatham County, North Carolina. In order to get a more complete picture from the fragments, researchers used a high-resolution surface scanner, creating a three-dimensional model of the reconstructed skull, using the more complete skulls of close relatives to fill in the missing pieces.
231 million years ago at the dawn of the Late Triassic, North Carolina was a warm, moist equatorial area, just beginning to break apart from the Pangean super continent.
“Fossils from this time period are extremely important to scientists because they record the earliest appearance of crocodylomorphs and theropod dinosaurs, two groups that first evolved in the Triassic period, yet managed to survive to the present day in the form of crocodiles and birds,” says Lindsay Zanno, assistant research professor at NC State, director of the Paleontology and Geology lab at the museum, and lead author of a paper describing the find. “The discovery of Carnufex, one of the world’s earliest and largest crocodylomorphs, adds new information to the push and pull of top terrestrial predators across Pangea.”
The Late Triassic was a busy time for land predators. Earlier cousins of the ancient crocs would have hunted alongside the earliest theropod dinosaurs in the Southern Hemisphere, and there was only so much prey to go around. Up north, however, it was large-bodied crocodylomorphs like Carnufex vying for the position of top predator, rather than dinosaurs.
By the end of the Triassic, the large crocodyloporphs were ceding ground to theropod dinosaurs, who went on to occupy the top predatory spots for the next 135 million years. Only smaller-bodied crocodylomorphs, closer to modern crocodilians, survived.
“As theropod dinosaurs started to make it big, the ancestors of modern crocs initially took on a role similar to foxes or jackals, with small, sleek bodies and long limbs,” says Susan Drymala, graduate student at NC State and co-author of the paper. “If you want to picture these animals, just think of a modern day fox, but with alligator skin instead of fur.”
The vestiges of these early adaptations can be seen today. Rather than walk on large hind legs, modern crocodiles and alligators are exclusively quadrupedal, retaining the longer, slimmer bodies of the Late Triassic. Though they typically prefer to crawl around on their bellies, modern crocodile limbs are actually quite long, when they can be bothered to stand up straight (usually reserved for the pursuit of prey).