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Scientists Discover What May be Oldest Dinosaur

Dec 05, 2012 03:43 AM EST

Scientists have found fossilized bones that likely belonged to the earliest known dinosaur, which was about the size of a Labrador retriever.

The new species, named Nyasasaurus parringtoni, was discovered near Tanzania in the 1930s. "Nyasa" is named for the present-day Lake Nyasa in Tanzania, where the bones were found. The term "saurus" represents lizard. "Parringtoni" is named for paleontologist Rex Parrington, from University of Cambridge, UK, who first found the fossilized bones.

Until now, it was thought that the dinosaur era began around 230 million years ago during the Late Triassic period. But the new finding suggests that the dinosaur lineage appeared 15 million years before the earliest known dinosaur specimens such as Eoraptor and Herrerasaurus were described.

"If the newly named Nyasasaurus parringtoni is not the earliest dinosaur, then it is the closest relative found so far," lead author of the study Sterling Nesbitt, from the University of Washington, said in a statement.

Nesbitt and his colleagues found an upper arm bone (humerus) and six vertebrae among the dinosaur fossils. They determined that the animal stood upright, walking on two legs and measured around seven to 10 feet in length with a five foot-long tail. It was three feet tall at the hip and weighed between 45 and 135 pounds.

The dinosaur species lived between 240 million and 245 million years ago (during the Middle Triassic period), when the world's continents were joined in the landmass called Pangaea. Tanzania was part of southern Pangaea. The discovery of the fossilized bones does not mean that the dinosaurs originated from Tanzania, researchers said.

Nyasasaurus parringtoni's age hints that the dinosaurs were part of a large diversification of archosaurs - animals that include pterosaurs, crocodiles and their relatives - which lived during the Triassic period 250 million to 200 million years ago.

Further analysis of the bones revealed that the newly-found specimens had a number of characteristics that are common to early dinosaurs and their close relatives. For instance, bone tissues in the humerus have been laid in a haphazard manner and not in an organized way. This signifies rapid growth, a feature that is commonly found in all early dinosaurs and their close relatives.

"We can tell from the bone tissues that Nyasasaurus had a lot of bone cells and blood vessels," said co-author Sarah Werning at the University of California, Berkeley, who did the bone analysis. "In living animals, we only see this many bone cells and blood vessels in animals that grow quickly, like some mammals or birds."

The research team also noticed that the upper arm bone had an enlarged deltopectoral crest, which anchors the upper arm muscles. This feature is also common to all early dinosaurs.

Although the fossilized bones represent the earliest known dinosaur, it is unlikely that the dinosaur was the mother or father of all the other dinosaurs and birds. The dinosaur could have possibly belonged to a group that lived for a short period and became extinct, co-author of the study Paul Barrett, from Natural History of Museum, told Discovery News.

The findings of the study are published in the journal Biology Letters.

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