The dinosaur, described in the latest Royal Society Biology Letters, was unearthed near present-day Lake Nyasa in Tanzania. It is named Nyasasaurus parringtoni, which combines the name Nyasa with the term for lizard. The name also honors Rex Parrington, a University of Cambridge paleontologist who first discovered the fossils.
Nyasasaurus walked the Earth about 10 million years before the current oldest dinosaur record holders -- such as swift-footed Eoraptor and Herrerasaurus -- suggesting that dinosaurs emerged in the Middle Triassic rather than in the latter years of that period. It also suggests that dinosaurs began as relatively small before some species grew to larger sizes.
"From the few preserved bones, we estimate Nyasasaurus to be about 10 feet long with a long neck," lead author Sterling Nesbitt, a University of Washington postdoctoral researcher in biology, told Discovery News. "These estimates are based on comparing the bones of Nyasasaurus to those of early dinosaurs and close relatives."
Co-author Paul Barrett; vice president of The Paleontological Society and head of the Natural History Museum's Division of Fossil Vertebrates, Anthropology and Micropaleontology; added that Nyasasaurus was also probably lightly built for a dinosaur (approximately 45-135 pounds), bipedal and with long hind legs. It lived in the southern portion of what was then the supercontinent Pangaea.
The scientists analyzed the dinosaur's fossilized bones, which are housed at the museum where Barrett works, as well as at the South African Museum in Cape Town. They have been in storage for at least 80 years. The late paleontologist Alan Charig named the specimen, but was unable to publish his report on the animal before he died. Charig is listed as a co-author of the current study.
The new paper gets to the heart of what a dinosaur is.
Barrett explains that dinosaurs are distinguished from other reptiles, in part, by rapid growth and certain bone characteristics.
"We can tell from the bone tissues that Nyasasaurus had a lot of bone cells and blood vessels," co-author Sarah Werning of UC Berkeley, explained. "In living animals, we only see this many bone cells and blood vessels in animals that grow quickly, like some mammals or birds."
She continued, "The bone tissue of Nyasasaurus is exactly what we would expect for an animal at this position on the dinosaur family tree. It's a very good example of a transitional fossil; the bone tissue shows that Nyasasaurus grew about as fast as other primitive dinosaurs, but not as fast as later ones."
An upper arm enlarged mass of bone, called an elongated deltopectoral crest, was also identified. It is another common feature of all early dinosaurs.
Some paleontologists have proposed that dinosaur diversity burst onto the scene in the Late Triassic. The new study refutes that idea, instead suggesting that dinosaurs were part of an earlier, large diversification of archosaurs, which were the dominant land animals during the Triassic period 250 million to 200 million years ago. They include dinosaurs, crocodiles and their kin.
Nyasasaurus, however, was found to be more closely related to birds than to crocodilians. Birds, in turn, "are the direct descendants of small, meat-eating dinosaurs," Barrett said.
The rocks that produced Nyasasaurus have also yielded giant fossil amphibians, fossils for reptiles, and fossils of cynodonts and dicynodonts, which were early mammal relatives.
Read more at Discovery News
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