How we revealed a new family tree for dinosaurs

New discoveries lead to new ideas - and sometimes the revival of old ones, such as the relationships between the earliest of the dinosaurs

Dinosaur buffs will have noticed some tremors propagating through the ether over the past couple of weeks. These followed from the publication of a new study, by Matthew Baron, David Norman and I, in which we proposed a radical rearrangement of the dinosaur family tree. This paper, published in the august journal Nature, provides a deliberate challenge to around 130 years of the palaeontological status quo. The essence of the paper is a simple one: for most of the past century the majority of scientists have regarded the long-necked sauropods, such as Diplodocus, and the carnivorous theropods, such as Tyrannosaurus, as more closely related to each other than either was to the other great group of dinosaurs, the vegetarian ornithischians, such as Stegosaurus.

However, our new study provides the first evidence for an alternative arrangement in which Stegosaurus and Tyrannosaurus become closer evolutionary cousins (and they and their relatives are combined in to a new group we name Ornithoscelida), with Diplodocus relegated to a more distant relationship with these other dinosaurs. A reader weary of regular pronouncements from dinosaur experts might simply shrug and say "so what?", as our knowledge of dinosaurs, and other extinct animals, is constantly being renewed and updated, with new discoveries quickly falling off of the front pages to languish in the quiet backwaters of academe. These types of adjustments to evolutionary trees might appear trivial, but our study, and many others like it, have a broader relevance that goes beyond their immediate impact. Establishing the interrelationships of animals, plants, fungi and bacteria to each other, to build a great tree of life, forms the basis of all biological science, for reasons I'll try to make clearer below. As a result, constant efforts are being made to build and refine evolutionary trees so that they depict the best-supported hypotheses of relationships among all living (and once-living) things.