image: Based on an analysis of how Tawa relates to other early dinosaurs, researchers hypothesize that dinosaurs originated in what is now South America and soon after diverged into ornithischians (like Triceratops), sauropodomorphs (like Apatasaurus) and theropods (like Tyrannosaurus rex), before dispersing across the Triassic world more than 220 million years ago. The theropods evolved into modern-day birds, although Tawa split off from the ancestral branch early on and was not a direct bird ancestor. This image relates to an article that appeared in the Dec. 11 issue of Science, published by AAAS. The study, by Dr. Sterling Nesbitt of the American Natural History Museum in New York, NY, and colleagues, was titled, "A Complete Skeleton of a Late Triassic Saurischian and the Early Evolution of Dinosaurs." view more
Credit: Zina Deretsky, National Science Foundation