Fossil sheds light on the murky, early period of dino evolution

Dinosaurs first appeared on Earth about 230 million years ago. Those were the Pangea days, when all land on the planet was condensed in one supercontinent. After showing up on the scene, dinosaurs split into three lineages: theropods, sauropods and ornithischians. But when did they split? Did they split in the days of the supercontinent, or after? A new fossil (of a creature named Tawa hallae), suggests the split occurred soe time around 215 million years ago, soon after dinosaurs appeared, and when Pangea still existed. (NY Times)