An enormous crocodile ancestor with blade-like teeth walked on two legs and was at the very top of North America's food chain 231 million years ago, according to a new study.
Named "Carolina Butcher" (Carnufex carolinensis), the newly discovered toothy beast reveals that predecessors of today's crocodiles -- crocodylomorphs -- were top predators in North America prior to the reign of dinosaurs.
Carolina Butcher, described in the latest issue of the journal Scientific Reports, lived up to its horror movie-style name.
"Carnufex lived in what is now North Carolina around the time the supercontinent Pangea was breaking apart," lead author Lindsay Zanno told Discovery News. "The skull of Carnufex is slender and long-snouted with dozens of blade-like teeth. For all practical purposes, this was an animal skillfully adapted for slicing flesh from the bones of its victims."
Zanno is an assistant research professor at North Carolina State University and director of the Paleontology & Geology Research Laboratory at the North Carolina Museum of Natural Sciences. She and her colleagues recovered the remains of Carolina Butcher from the Pekin Formation in Chatham County, North Carolina. When the crocodylomorph was alive during the beginning of the Late Triassic, this area was a wet and warm equatorial region.
The researchers created a detailed 3-D model of Carolina Butcher's skull using a high-resolution surface scanner to digitize each unearthed fossil from what's left of the animal's head. This high tech model and the croc's other remains suggest that the carnivore was at least 9 feet tall. Because its forelimbs were so short compared to its skull, the researchers suspect that the carnivore walked on two legs a/la T. rex.
The scientists don't yet have hard evidence -- such as stomach contents or unique bite marks on other animal fossils -- indicating what Carolina Butcher hunted. Based on other known animals from this area at the time, however, the scientists believe likely prey candidates were aetosaurs (armored reptiles) and dicynodonts (large-bodied early relatives of mammals). These animals themselves were formidable.
Carolina Butcher was not the only meat-eater around, either.
"The Triassic was a bit of an ecological Twilight Zone: too few plant eaters and an over abundance of predators meant that the hunters often became the hunted," Zanno said.
She explained that other major terrestrial predators roaming around this area in North America at the time were rauisuchids, which had skulls that looked a lot like tyrannosaurs. Phytosaurs, which resembled today's crocodiles but were actually more distant relatives, hunted in the water and sometimes even killed rauisuchids, perhaps when an unlucky one strayed too close.
As time went on, the pileup of predators dramatically changed after a major extinction event occurred.
"By the end of the Late Triassic, all of the large predators on land, except dinosaurs, had been wiped from the face of the planet," Zanno explained. "Scientists aren't yet sure why, but the prevailing hypothesis is that the absence of other competitors gave theropods (carnivorous dinosaurs) a big boost on the Mesozoic playing field."
Smaller ancestors of crocodiles made it through the extinction event, and later on found their ecological niche. They re-evolved into the larger sizes exhibited by crocodiles and alligators today.
Diego Pol of Argentina's Museo Paleontológico Egidio Feruglio also studies early predators. He told Discovery News that Zanno and her team's discovery "fills an important gap in the early evolution of crocs."
Even with this filled gap, intriguing questions remain. For example, the common ancestor of the dinosaur/bird line and the crocodile line is still unknown. The researchers suspect that it lived about 250 million years ago. The animal must have been quite hearty, since many of its later relatives survived multiple extinction events and became some of the planet's most impressive predators.
"So much remains to be learned about ecosystems in the Triassic and their recovery from mass extinction events," Zanno said. "It's a great time to be working on this part of Earth's history."