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Dinosaur discoveries wow Boston

Dinosaur discoveries wow Boston
By BBC News Online's Jonathan Amos

Sensational fossil discoveries were unveiled on Monday, including the most primitive wishbone yet found in a dinosaur.

Also presented was an exquisite skull from a tiny crocodile that could help provide vital new evidence on when the landmasses of Africa and South America split to take up their current positions on the planet's surface.

The finds were described by Paul Sereno, one of the world's leading dino hunters, at the annual meeting of the American Association for the Advancement of Science in Boston.

Dr Sereno, from the University of Chicago, told the meeting that science was on the cusp of a new era in dinosaur discovery. He said Africa, in particular, would soon yield extraordinary specimens that would enable scientists to explain more fully how these great beasts evolved.

Original role

The wishbone, or furcula, is significant because it informs the debate on whether birds evolved from dinosaurs; until recently the V-shaped bone was thought to be a unique feature in birds.

The fossil furcula shown off by Dr Sereno was part of the skeleton of an 11-metre-long predator known as a spinosaur. Although the 110-million-year-old wishbone is not the oldest known to science, the creature from which it came had a very deep lineage.

"There is an allosaur furcula that is 150 million years old but this is from the chest of an animal with a more ancient origin.

"We are trying to nail down when the wishbone as fused clavicles first appeared in theropod (bipedal meat-eaters) evolution. So, this new furcula is now the most primitive one ever found.

"That's not to say that spinosaurs are closely related to birds; the wishbone, like many other adaptations, had nothing to do with flight in its original role. Only later did it become a flexible spring between the shoulder blades of flying birds - a totally different role."

Duck muzzle

The spinosaur was uncovered in Niger, Africa, on what Dr Sereno said was an amazing expedition which brought away 20 tonnes of fossils and rock.

The spinosaur specimen was found within 80 kilometres of the site of the dwarf crocodile skull also displayed at the AAAS meeting.

This fossil came from a 60-centimetre-long animal that has yet to receive a formal classification but which has been dubbed the "duck croc" because of its unusual jaws.

"It has a muzzle that looks like a duck," Dr Sereno said. "It's very broad but the upper jaw hangs over the lower jaw, so viewed from the side you don't even see the lower jaw. There's no interaction between the teeth at all."

Dr Sereno thinks this arrangement may have enabled the animal to catch specific kinds of prey, "such as a frog or a type of fish". Other features suggest it spent more time out of the water than it. "I think it was more land-adapted - living on the bank, catching frogs."

Dr Sereno said the 110-million-old skull and other finds from Africa and South America could upset current views on how the once giant supercontinent of Gondwanaland broke apart many millions of years ago.

'New frontier'

He said there was a big argument over whether Africa split first, meaning South American animals and plants were more closely related to fauna in India, Madagascar and Antarctica.

"I think we're going to overturn that now with some of the evidence we have dug up," he said. "It's going to show that Africa and South America were very closely related up to about 90 million years ago."

Dr Sereno said he had many more discoveries in the pipeline that would eventually be submitted to journals for the science community to review. These include new predatory dinosaurs from India and Africa that hail from the Cretaceous Period (146 to 65 million years ago).

Dr Sereno said Africa was the "new frontier" in dino research. Specimens were required from this under-researched part of the world to fill in important gaps in our knowledge.

"To understand how plate techtonics (the movement of the continents) affected the evolution of a major group like dinosaurs, we need Africa."