What ate dinosaurs?: Old crocs
ONE answer to the question, “What ate dinosaurs?” is, obviously, “Other dinosaurs.” Theropod predators like Tyrannosaurus and Allosaurus loom large in the imagination of every lover of prehistoric monsters, and their animatronic fights with the likes of Diplodocus and Stegosaurus are the stuff of cliché. Science, though, tries to look beyond the obvious, and at this year’s meeting of the Society of Vertebrate Palaeontology, held in Las Vegas, some of the speakers asked whether the top predators of the Mesozoic era really were all dinosaurs. Their conclusion was “no”. Another group of reptiles, until recently neglected, were also important carnivores. And it is a group that is still around today: the crocodiles.
That the past role of crocodiles (or, strictly, crocodilians, since they came in many sizes and shapes, not all of which resemble the modern animals) has been underestimated was suggested a few years ago by Paul Sereno. Dr Sereno, a palaeontologist at the University of Chicago, uncovered a crocodile-dominated ecosystem from about 100m years ago (the middle of the Cretaceous period), in what is now north Africa. Besides water-dwelling giants similar to (though much bigger than) today’s animals, he found a range of forms including vegetarians and species that ran on elongated legs—more like dogs than crocodiles. That discovery has prompted other fossil hunters to look elsewhere. As a result, even the well-studied rocks of North America are revealing that dinosaurs did not have it all their own way in the ecosystems of the Mesozoic—as Stephanie Drumheller of the University of Iowa and Clint Boyd of the University of Texas at Austin explained to the meeting.
The Cretaceous equivalent of zebra and antelopes—the victim species in every wildlife documentary about the dramas of the African savannah—were herbivorous dinosaurs called ornithopods. Frequently, these were taken by theropods. But not always. When Ms Drumheller and Mr Boyd examined the bones of juvenile upper-Cretaceous ornithopods dug up in Utah they saw marks on one skeleton that looked suspiciously like those modern crocodiles inflict when biting and tearing at their prey. On examining these marks more closely, they found a crocodilian tooth stuck in one of them.