Meet the dinosaur so ancient it may be a missing link

Paleontologists have identified what may be the earliest specimen of a dinosaur on record, a discovery that could reset the clock on when these animals first emerged. The new species, Nyasasaurus parringtoni, is so ancient that researchers are reluctant to declare it a true dinosaur. The dog-sized biped may actually represent a ‘missing link' — what would be the closest known relative to dinosaurs.

The fossilized remains of Nyasasaurus were actually discovered in Tanzania during the 1930s, but it was only recently that a more rigorous analysis of the bones was conducted. The project was led by Sterling Nesbitt, a postdoctoral biology researcher at the University of Washington.

Nyasasaurus lived in the Middle Triassic, about 10 to 15 million years earlier than other dinosaurs (what was the Late Triassic period). The finding now indicates that dinosaurs — assuming that that's what this is — first emerged around 245 to 250 million years ago, a time when the Earth's landmass consisted of the giant Pangaea supercontinent. The finding suggests that dinosaurs were not a dominant vertebrate group during their early evolution.

Meet the dinosaur so ancient it may be a missing linkS

The herbivore stood upright, was about seven to 10 feet in length (two to three meters), and stood three feet up from the hip (one meter). It likely weighed between 45 and 135 pounds (20 to 60 kilograms).

Interestingly, some paleontologists have suggested that, based on such evidence as fossilized footprints and other clues, dinosaurs may very well have existed during the Middle Triassic. The discovery of Nyasasaurus now adds weight to this hypothesis.

But the researchers note that if Nyasasaurus is not the earliest dinosaur, then it is the closest relative found so far. Nesbitt's team is hoping that further research will shed some light on the possibility.

What they do know, however, is that the new species features a number of characteristics consistent with early dinos and their close relatives. For example, the bone tissues in the upper arm were woven haphazardly — an indication of rapid growth, what is a common feature of dinosaurs and their close relatives. It also had an enlarged crest in its upper arm bone, which would have anchored its upper arm muscles; this elongated deltopectoral crest is also common to early dinosaurs. Additionally, it had a lot of bone cells and blood vessels, what's only seen in birds and some mammals.

Consequently, the paleontologists say it's a good example of a transitional species — a link between dinosaurs and their lizard-like ancestors.

The researchers conclude their study by suggesting that dinosaurs were part of a large diversification of archosaurs, a group that dominated the Triassic period 250 million to 200 million years ago.

The entire study can be read at Biology Letters.

All images: Natural History Museum.