For more than a century, the placement of dinosaurs on the branches of their family tree has been based on the shape of their hips.
This classification has now been radically challenged by proponents of a new tree which, if accepted, swaps large subfamilies around, sheds new light on dinosaurs evolution and suggests they may have originated not in South America, as widely assumed, but perhaps in some Northern Hemisphere locality such as Scotland.
A Victorian paleontologist, Harry Seeley, declared in 1888 that dinosaurs should be divided into the bird-hipped (Ornithischia) and the lizard-hipped (Saurischia) categories that have been accepted ever since.
Under this system, the heavily armored stegosaurs and ankylosaurs are placed on the Ornithischian branch of the family tree. The Saurischian branch includes both sauropods like the herbivorous diplodocus, and theropods like the meat-eating tyrannosaurs.
This longstanding classification has now been disputed by Matthew G. Baron of the University of Cambridge. Mr. Baron is a graduate student and his rewriting of the dinosaur family tree is a project to attain his Ph.D. But his ideas are supported by his two supervisors and co-authors, David B. Norman of the University of Cambridge, and Paul M. Barrett of the Natural History Museum in London, and by a prodigious database he has constructed of dinosaur anatomical features.
