`Young tyrannosaurs were careful predators`

Last Updated: Saturday, May 14, 2011 - 09:27

Washington: Their parents may have wielded
their massive strength and size to kill large prey, but young
tyrannosaurs were careful predators who relied on quickness
and agility rather than raw power, scientists have found.

Tyrannosaurs were that largest ever known dinosaurs that
roamed the earth some 65 million years ago.

An international team of scientists who investigated the
youngest and most complete skull of a 70-million-year-old
tyrannosaur, unearthed five years ago in the Gobi Desert in
Mongolia, believe the young animals were not powerful like
their parents and fed on smaller preys.

The skull was found as part of a nearly complete
skeleton, missing only the neck and two-thirds of the tail,
which belonged to a Tarbosaurus, a fearsome predator roughly
as large as its closest known relative, Tyrannosaurs rex.

"We knew that adult Tarbosaurus were a lot like T rex,"
researcher Takanobu Tsuihiji, of the National Museum of Nature
and Science in Tokyo, was quoted as saying by LiveScience.

Based on careful analysis of the microstructure of the
leg bones, researchers estimated this predator was only 2 to 3
years old when it died.

It was about 9 feet long, about 3 feet high at the hip
and weighed about 32 kg. In comparison, an adult Tarbosaurus
was 35 to 40 feet long, 15 feet high, weighed about 6 tons and
probably had a life expectancy of about 25 years.

CAT scans of the immature 11.4-inch skull revealed that
it was far more delicate than an adult`s and was incapable of
handling the kinds of twisting and stress that the reinforced
skull of a grown-up Tarbosaurus could.

"Adults show features throughout the skull associated
with a powerful bite -- large muscle attachments, bony
buttresses, specialised teeth," Tsuihiji explained.

In comparison, "the juvenile is so young that it doesn`t
really have any of these features yet, and so it must have
been feeding quite differently."

This suggests "the younger animals would have taken
smaller prey that they could subdue without risking damage to
their skulls," Tsuihiji explained.

"This spectacular specimen provides us with a really
clear window into how these dinosaurs changed over the course
of their lives," Witmer told LiveScience.

"Tarbosaurus is found in the same rocks as giant dinosaurs
like the long-necked sauropod Opisthocoelicaudia and the
duckbill hadrosaur Saurolophus," said researcher Mahito Watabe
of the Hayashibara Museum of Natural Sciences in Okayama, who
led the expedition that uncovered the new skull.

"But the young juvenile Tarbosaurus would have hunted
smaller prey, perhaps something like the bony-headed dinosaur
Prenocephale."

This range of feeding strategies could have been one of
the secrets of success for tyrannosaurs, strengthening their
role as the dominant predators during their time, Witmer said.
The scientists detailed their findings in the Journal of
Vertebrate Paleontology.

PTI



First Published: Saturday, May 14, 2011 - 09:27

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