Paleontologists say they've uncovered the fossil of an ancestor of crocodiles that was a predator, capable of walking on its back legs and standing nine feet tall, so fearsome that they've dubbed it the "Carolina Butcher."

The creature, Carnufex carolinensis, was probably one of the top predators in North America before the arrival of the dinosaurs, with strong jaws that could chomp through mammals and even small armored reptiles, they say. The Latin Carnufex translates to butcher, Carolinensis for the region where it was found.

Paleontologists from North Carolina State University and the North Carolina Museum of Natural Sciences, writing in the journal Scientific Reports, described unearthing parts of the skull, spine and upper forelimb of Carnufex from the Pekin Formation in the state's Chatham County.

Dated to around 230 million years ago, the fossil of the newly identified species yields new insights into crocodilian evolution, they say.

"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 study lead author Lindsay Zanno.

It comes from a time when North Carolina was a tropical equatorial region just beginning to break away from the giant supercontinent Pangea, the researchers explain.

Until the fossil discovery, it was unclear if early ancestors of crocodiles were competing for a top predator role in North America before the reign of the dinosaurs, Zanno says.

That's what made the finding of the "Carolina Butcher" so exciting, she says.

"Even before we had prepared the bones from the rock, we knew we had a unique and bizarre new species," she says, describing a skull highly decorated with grooves and bumps, making it unlike anything seen before.

"After removing all the bones, we were excited to discover that this animal is a bit of a Frankenstein."

Carnufex was much larger than modern day crocodiles, and had longer hind legs than the short limbs of today's species, suggesting it could get about on its hind legs using a walking gait, the researchers say.

The discovery also proves the evolutionary lineage of crocodiles extends further back in the past then previously thought, experts say.

"It pushes back the date of crocodylomorphs in the fossil record," says Daniel Mulcahy of the Smithsonian National Museum of Natural History. "And because of its size, presumed diet and body shape, [Carnufex] changes our thinking on what these early crocodiles looked like and what they did."

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