Smithsonian.com

The skeleton of Panphagia protos, from the new PLoS paper.

The long-necked sauropod dinosaurs were among the most massive creatures to have ever evolved (their immensity only surpassed by the blue whale), but like all dinosaurs their early relatives were quite small. A newly announced early sauropodomorph dinosaur, Panphagia protos, is one of these early relations and it fills in an important gap in sauropod evolution.

About 230 million years ago in what is now Argentina, the first dinosaurs scurried through the forest—creatures that had short arms, sharp-toothed jaws, and ran on two legs. Eoraptor was one such early dinosaur, and it was found in the early 1990s in the same area in which Panphagia was discovered. In fact, Panphagia looks more like Eoraptor than it does its later gigantic cousins Apatosaurus and Brachiosaurus, but that it is a sauropodomorph is established by similarities between it and another early sauropodomorph called Saturnalia. Panphagia is definitely closer to Saturnalia than to Eoraptor, and the new genus represents an early stage of evolution of the sauropod dinosaurs.

The discovery of Panphagia has some important implications, and it may become even more important as several as-yet-undescribed dinosaurs mentioned in the paper come to light. Not only does it offer clues about how the sauropod branch of the dinosaur family tree originated, but it hints that there are even older dinosaurs yet to be found. Since Panphagia lived alongside, but was different from, other early dinosaurs like Eoraptor, it can be hypothesized that there was an even earlier divergence between the early ancestors of sauropods and theropods. The common ancestor for all dinosaurs would be even older, and so the new discovery suggests that dinosaur evolution reached back deeper into the Triassic than the evidence previously supported. For now, though, Panphagia is a beautiful transitional fossil that helps us understand how the gigantic sauropods evolved.