Friday, 9 March 2012

New Evidence That Predatory Dinosaurs Were Also Scavengers

The 75 million year old Velociraptor fossil. The black arrows indicate
 the position of the pterosaur bone shard while the white indicated
the broken rib. The bulge of bone around the damaged area shows
 that the wound had begun to heal before the time of death
One of the greatest debates in palaeobiology is whether the world famous Tyrannosaurus rex was primarily a hunter or a scavenger. Its massive jaws and powerful legs suggests that it was designed for high speed chases in pursuit of prey, resulting in death from a single, bone shattering bite. Yet other palaeobiologists believe that it was too slow to hunt effectively and therefore fed off the carcasses of other creatures. The equally famous Velociraptor has shown that dinosaurs may also have been scavengers.

An international research team led by David Hone from University College, Dublin, excavating at the Gobi Desert in Mongolia, one of the best locations for collecting top quality dinosaur fossils, have found a 75 million year old Velociraptor fossil with some rather unexpected remains in its stomach: a bone from a pterosaur with a wingspan of over two metres. A small, feathered dinosaur, despite its predatory nature and sickle claws would simply have been unable to tackle, a healthy, fully grown aerial giant.

'It would be difficult and probably even dangerous for the small theropod dinosaur to target a pterosaur with a wingspan of 2 meters or more, unless the pterosaur was already ill or injured' said Dr Hone. The team concluded that the Velociraptor had eaten flesh from a fallen pterosaur carcass, simultaneously ingesting the 75 mm bone shard. Analysis of the bones showed that the dinosaur died shortly after due to a broken rib rather than a punctured stomach.

It is likely that its injury forced it to scavenge.'Gut contents are pretty rare and pterosaur bones are rather fragile and don't preserve well, so it is an unusual find,' added Dr Hone. These kinds of fossils are rare enough without the addition of stomach contents and a level of preservation high enough to be able to reconstruct the final chapter of a life story, making this find very important. While it does not show whether predatory dinosaurs were primarily scavengers, it does show that they probably resorted to feeding off of carrion if the situation was dire enough.