Kostensuchus atrox, a large Cretaceous crocodyliform from Patagonia

Paleontologists have announced the discovery of a large, meat-eating relative of modern crocodiles that lived about 70 million years ago in what is now southern Argentina. The species, named Kostensuchus atrox, was described from a remarkably complete fossil found in the Chorrillo Formation in Patagonia. Measuring roughly 3.5 metres in length and estimated at about 250 kilograms, the animal had a broad, powerful skull and serrated teeth adapted for slicing flesh, leading researchers to conclude it was one of the top predators of its ecosystem and likely preyed on medium-sized dinosaurs.

The fossil, unearthed in March 2020 and prepared over subsequent months, includes a well-preserved skull, jaws and multiple postcranial bones. "The new fossil unearthed in this formation is largely intact, including a skull and jaws with visible details, as well as multiple bones from the body," said Fernando Novas, a paleontologist involved in the study. Based on comparisons with modern caimans and alligators, the team estimated an overall body length of about 11.5 feet and a weight near 551 pounds.

Anatomical features distinguish Kostensuchus from living crocodilians and point to a more...