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Species called missing link

Scientists reveal dinosaur discovery

South African paleontologist Adam Yates, with bones of the Aardonyx celestae, said the species occupied a 'very significant position in the family tree of dinosaurs.' South African paleontologist Adam Yates, with bones of the Aardonyx celestae, said the species occupied a "very significant position in the family tree of dinosaurs." (Reuters)
By Celean Jacobson
Associated Press / November 12, 2009

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JOHANNESBURG - A newly discovered dinosaur species that roamed about 200 million years ago might help explain how the creatures evolved into the largest animals on land, scientists in South Africa said yesterday.

The Aardonyx celestae was a 23-foot-long small-headed herbivore with a huge barrel of a chest. It walked on its hind legs but also could drop to all fours, and scientists said that could prove to be a missing evolutionary link.

This is a species “that no one has seen before and one that has a very significant position in the family tree of dinosaurs,’’ said Australian paleontologist Adam Yates.

Yates, who is based at the University of the Witwatersrand’s Bernard Price Institute for Paleontological Research, led the research with several local and international scientists.

Their findings were published yesterday in the Proceedings of The Royal Society B, a London-based peer-reviewed journal.

The Aardonyx celestae species dates to the early Jurassic period. Yates said the creature found in South Africa stood nearly 6 feet high at the hip and weighed about 1,100 pounds.

The species shares many characteristics with the plant-eating herbivores that walked on two legs, Yates said. But the new species also has similar attributes to dinosaurs known as sauropods, or brontosaurs, that grew to massive sizes and walked on all fours with long necks.

“The discovery of Aardonyx helps to fill a marked gap in our knowledge of sauropod evolution, showing how a primarily two-legged animal could start to acquire the specific features necessary for a life spent on all fours,’’ said Paul Barrett, a paleontologist at the British Natural History Museum who assisted on the dig that led to the finding.

Why and how dinosaurs grew into such massive creatures is a question that scientists have been trying to answer.

Walking on all fours allowed animals to carry more weight, and size was often their only defense against sharp-toothed carnivores, said one of the report’s co-authors, Matthew Bonnan of Western Illinois University.

The discovery of the new species was made by postgraduate student Marc Blackbeard.