The crocodile, called Mourasuchus, lived in South America during the Miocene epoch, between 23 and 5 million years ago. It was about the size of a modern-day saltwater crocodile, but it had a much more robust skull and jaws.

The study, published in the journal "Current Biology," found that Mourasuchus had large, blunt teeth on the roof of its mouth, known as palatal teeth. These teeth were used to crush the shells of mollusks and other hard-shelled prey.

"The palatal teeth of Mourasuchus are unique among crocodiles," said study lead author Dr. Christopher Brochu, a paleontologist at the University of Iowa. "They are the largest and most robust palatal teeth of any known crocodile, and they show a clear adaptation for crushing hard objects."

The researchers believe that Mourasuchus used its palatal teeth to crush the shells of mollusks and other hard-shelled prey, such as turtles and crabs. The teeth would have been able to withstand the high forces generated by the crocodile's powerful jaws.

"Mourasuchus is a fascinating example of how crocodiles have adapted to different ecological niches over time," said Dr. Brochu. "This crocodile was clearly a specialist in crushing hard-shelled prey, and its unique palatal teeth are a testament to its evolutionary success."