The creature is either the oldest known dinosaur yet discovered or a close relative to the oldest currently known specimen.

What may be the most ancient dinosaur ever found or at least a very close relative to the oldest currently known examples could push the appearance of the awesome beasts back to 243 million years ago.
Paleontologist Rex Parrington of the University of Cambridge in England discovered the fossil in the early 1930s, preserved in a rock formation known as the Manda Beds in Tanzania's Ruhuhu Valley. Now, a team of scientists has taken a fresh look at Nyasasaurus parringtoni. It lived during the Anisian age of the Middle Triassic period, about 10 million to 15 million years earlier than the oldest confirmed dinosaurs. The finding suggests dinosaurs evolved and diversified over a longer time frame than scientists thought, the team reports online December 4 in Biology Letters.
So far only fragments of the creature's backbone and upper arm bone have been found, but these bear telltale features of dinosaurs, such as rapid bone growth. More fragments are needed to determine whether the fossil is in fact the oldest dinosaur or a member of the nearest sister group.
At 2 to 3 meters long and no more than 1 meter tall, Nyasasaurus was hardly a king of the beasts. It would have been slightly larger than a golden retriever but with a very long tail, says Sterling Nesbitt, a paleontologist at the University of Washington in Seattle. Nesbitt and colleagues estimate that the creature weighed about 20 to 60 kilograms.
The team examined the fossil's structure and microscopic anatomy and then compared it with members of known animal family trees. Computer analyses showed that Nyasasaurus was either part of the dinosaur lineage or an as-yet-unknown group that's even closer than dinosaurs' nearest currently known relatives, silesaurids.

Source: Science News