Size and Weight:
Announced to the world in December of 2012, Nyasasaurus is an exceptional find: a dinosaur that lived in the southern continent of Pangaea during the early Triassic period, about 243 million years ago. Why is this such stunning news? Well, scientists previously believed that the earliest true dinosaurs (such as Eoraptor and Herrerasaurus) arose in middle Triassic South America, at a remove of 10 million years and 1,000 or so miles.
There's still a lot we don't know about Nyasasaurus, but what we do know points to an unmistakably dinosaurian lineage. This reptile measured about 10 feet from head to tail, which may seem enormous by Triassic standards, except for the fact that fully five feet of that length was taken up by its unusually long tail. Like other early dinosaurs, Nyasasaurus clearly evolved from a recent archosaur ancestor, though it may have represented a "dead end" in dinosaur evolution (the "true" dinosaurs we all know and love still being descended from the likes of Eoraptor).
One thing about Nyasasaurus that remains a mystery is this dinosaur's diet. The earliest dinosaurs preceded the historic split between saurischian and ornithischian varieties (saurischians were either carnivorous or herbivorous, and all ornithischians, as far as we know, were plant-eaters). It seems most likely that Nyasasaurus was omnivorous, and its descendants (if any) evolved in more specialized directions.
It may yet turn out that Nyasasaurus is technically classified as an archosaur rather than a true dinosaur. This would not be an unusual development, since there's never a firm line that separates one type of animal from another in evolutionary terms (for example, which genus marks the transition from the most advanced lobe-finned fish to the earliest tetrapods, or the small, feathered, fluttery dinosaurs and the first true birds?)