Tyrannosaurs: history's most fearsome… scavengers?

he terrible lizards were not above scavenging for a free lunch, it seems.

Tooth marks found on the humerus of a plant-eating dinosaur found in Mongolia shows that a large tyrannosaur deftly removed the meat from the 0.9-metre-long bone, yet the rest of the skeleton showed no sign it had been attacked by a predator. That's a sure sign of scavenging, says David Hone of the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, China.

The dietary preferences of Tyrannosaurus rex, the biggest tyrannosaur, became a matter of debate in the early 1990s. Jack Horner of the Museum of the Rockies in Bozeman, Montana, suggested that despite its powerful jaws, T. rex's puny arms and massive legs would have made it an ineffective and ponderous predator. Nevertheless, palaeontologists tend to believe – as do the public, after Jurassic Park – that T. rex was an active predator.

Handy snack

Hone Watabe and Mahito Watabe of the Hayashibara Museum of Natural Sciences in Okayama, Japan, report that three distinctive types of tooth marks on the 70-million-year-old bone match the pattern and shape of the teeth Tarbosaurus, an Asian tyrannosaur nearly as big as T. rex. The marks are distributed in ways that indicated the tyrannosaur was biting to carve off chunks of flesh rather than attacking live prey.

Because the rest of the skeleton was largely intact and showed no bite marks, they suggest that a flood had buried its body in riverside deposits, leaving only the forelimb exposed for the hungry Tarbosaurus.

Scavenging makes just as much sense for big fearsome predators as it does for less scary ones, says tyrannosaur specialist Thomas Holtz of the University of Maryland at College Park. "Meat that doesn't fight back is a lot easier to get," he says.

Holtz was intrigued by the evidence that the Tarbosaurus selectively sliced meat from the bone with its teeth, rather than pulverising the bone and gorging itself.

Journal reference: Acta Palaeontologica Polonica, DOI: 10.4202/app.2009.0133

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