Researchers have discovered what may be the earliest dinosaur. Nyasasaurus parringtoni
was a Labrador retriever-sized dinosaur with a five foot-long tail. It weighed about 20 to 60 kilograms (45-135 pounds). Nyasasaurus
is from the Anisian (Middle Triassic, approximately 243 million years old) and predates all other dinosaurs by about 10 million years.
The researchers say the finding indicates dinosaurs likely appeared in the fossil record 10 million to 15 million years earlier than expected. It also suggests that dinosaurs were not a dominant vertebrate group during their early evolution. A research paper on the dinosaur was published here
in Biology Letters
Sterling Nesbitt, a University of Washington postdoctoral researcher in biology and lead author of the paper, says in a release, "If the newly named Nyasasaurus parringtoni is not the earliest dinosaur, then it is the closest relative found so far. For 150 years, people have been suggesting that there should be Middle Triassic dinosaurs, but all the evidence is ambiguous. Some scientists used fossilized footprints, but we now know that other animals from that time have a very similar foot. Other scientists pointed to a single dinosaur-like characteristic in a single bone, but that can be misleading because some characteristics evolved in a number of reptile groups and are not a result of a shared ancestry."
The fossilized bones - one humerus (upper arm bone) and six vertebrae - were collected in the 1930s from Tanzania. Tanzania would have been part of southern Pangaea during the time period Nyasasaurus
lived. The Pangaea landmass included Africa, South America, Antarctica and Australia.
Nesbitt also says, "Nyasasaurus
and its age have important implications regardless of whether this taxon is a dinosaur or the closest relatives of dinosaurs. It establishes that dinosaurs likely evolved earlier than previously expected and refutes the idea that dinosaur diversity burst onto the scene in the Late Triassic, a burst of diversification unseen in any other groups at that time."
Late paleontologist Alan Charig is included as an author on the research paper. Charig studied Nyasasaurus
for 50 years but was unable to publish his report on the animal before he died. The name "Parringtoni" is in honor of University of Cambridge's Rex Parrington, who collected the specimens in the 1930s.
Photo: Natural History Museum, London/Mark Witton