100-mln-yr-old fossil suggests link between South American and Aussie dinos

Washington, June 11 : A rare hundred-million-year old dino fossil found in Australia has led scientists to suggest a link between South American and Aussie dinosaurs.

According to a report in National Geographic News, the fossil belonged to a two-legged meat eater, or theropod, that is closely related to Megaraptor namunhuaiquii, a giant, big-clawed carnivore from Argentina.

The discovery could help redraw the world map during the dinosaur era, researchers said.

That's because the newfound Australian dinosaur shows that animals could travel across the prehistoric supercontinent of Gondwana during the Cretaceous period, about 145 to 65 million years ago.

This in turn suggests that Gondwana's Southern Hemisphere landmasses broke up later than traditionally thought.

The study is based on the unidentified theropod's arm bone, which was discovered at Dinosaur Cove in southeastern Australia in 1989.

"The fossil has unique features that solidly link it to the South American Megaraptor that was first described in 1998," said Nathan Smith of the University of Chicago's Field Museum.

"Megaraptor has a huge hand with a big (clublike) claw and a very strange forearm, so if you had to pick one bone to refer to, then the ulna (arm bone) might be that bone," he added.

The length of the fossil bone, 7.6 inches (19.3 centimeters), suggests the dinosaur was about half the size of Megaraptor.

This size difference could be because it is a smaller species or because it was a juvenile, according to Smith.

Previously scientists thought that Australian animals were isolated from life on other Gondwana landmasses during most of the Cretaceous because of geography and climate, the study authors said. "What we now have is demonstration that there must have been some kind of (animal) exchange between Australia prior to about a hundred million years ago," said Smith.

The new study also supports alternative models for the break up of Gondwana.

Traditionally, it was thought that Africa and South America separated from eastern Gondwana, which included Antarctica, Australia, India, and Madagascar-some 138 million years ago.

The alternative models show Africa separating first.

ANI