BioEd Online

Crocodiles are easily recognized by their long, toothsome snouts. But fossil hunters in Patagonia have found one that has a short, blunt nose and relatively few teeth. Experts say that its odd shape probably means it had a different diet to the fishy one favoured by other crocs, past and present.

A surprisingly short skull and two stumpy lower jaws were uncovered in Patagonia by Zulma Gasparini, a palaeontologist at Argentina's Museo de La Plata, and her colleagues. Features of the skull revealed that the new fossils were of Dakosaurus andiniensis, a marine crocodile known from only a few fragments found in Argentina. They show that D. andiniensis, which menaced the deep waters of the Pacific Ocean some 160 million years ago, had a bullet-shaped head that has surprised experts.

"Other vertebrate palaeontologists have been asking us whether this really is a crocodile," says Diego Pol, at Ohio State University, one of the two co-authors of the paper published online by Science¹.

Catch me if you can

Although some extinct terrestrial crocodiles were known to have short heads, until now all known marine crocodiles had long snouts. The skull also has a small number of large, serrated teeth, rather than the usual quota of many small, pointed ones.

Palaeontologists think that, like modern crocodiles, extinct marine forms swept their long, shallow jaws sideways to grab their slippery prey of fish or squid. D. andiniensis's stumpy head was probably not hydrodynamic enough to pull this off successfully.

"The big question is: what did they eat?," says Eric Buffetaut, a vertebrate palaeontologist at the National Centre for Scientific Research in Paris. He says D. andiniensis's large serrated teeth are better suited to cutting chunks off bigger prey than to grabbing whole fish. "It suggests they may have fed on other marine reptiles or large fish," he says, "but the only way to be sure is to find a fossil complete with stomach contents."