On The Menu : Finding a prehistoric supper and the creature who ate it : Some 75.3 million years ago, a dinosaur swallowed the Cretaceous equivalent of a turkey drumstick. It would be the predator's final feast.

Within days of eating that haunch, the dinosaur - a juvenile Gorgosaurus that stood 5 1/2 feet [ 1.68 meters ] tall at the hip - was dead in a river. Sediments rapidly covered much of the carcass and protected the dinosaur, and the dinner from decay.

The resulting fossil, unveiled in the Journal Science Advances, is the first tyrannosaur skeleton ever found with stomach contents still preserved inside, yielding an exquisite snapshot of its feeding behaviour.

The fossil also preserved much of the skull, pelvis and and left side of the Gorgosaurus's body.

Gorgosauruses were ancestral relatives of Tyrannosaurus rex, but this fossil doesn't contain a speck of the large herbivores on which adult tyrannosaurs feasted.

Instead, this Gorgosaurus ripped the hind limbs off two small feathered dinosaurs. The fossil provides the first direct evidence that tyrannosaurs changed what they ate as they aged, which paleontologists had predicted from existing fossil evidence.

'' With this specimen, we have physical proof that young tyrannosaurs not only fed on different animals then their adult counterparts, but they also attacked or dissected them differently,'' said Francois Therrien, the curator of dinosaur paleocology at the Royal Tyrrell Museum of Drumheller, Alberta and an author of the study.

Previously, discovered coprolites .... fossilized poop - and bones damaged by teeth or stomach acid show that adult tyrannosaurs feasted on large plant-eating dinosaurs such as Triceratops with bone crunching gusto.

But before they could take down megaherbivores, tyrannosaurs had to grow larger, and their skulls and teeth had to grow wide and robust enough to generate one of nature's most powerful bites.

Juvenile tyrannosaurs, however, had skinny skulls, narrow jaws, blade - like teeth and long legs.

Those traits had been interpreted as signs that young tyrannosaurs must have been nimble, an idea supported by the new fossil. [ Michael Greshko ]


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