Identity Crisis: New Hypothesis Suggests Radical Changes to the Dinosaur Family Tree

Although dinosaurs have been extinct for millions and millions of years, we continue to be fascinated by these ancient reptiles. Now, some of the most basic and widely accepted "facts" about dinosaurs are being challenged in light of a new research published in the journal Nature.

According to a report from New Scientist, H.G. Seeley divided dinosaurs into two different categories based on their pelvic bones: bird-hipped ornithischians like the herbivorous Stegosaurus and Triceratops, and lizard-hipped saurischians that includes carnivorous theropods like the Tyrannosaurus rex and long-necked herbivorous sauropodomorphs like the Apatosaurus.

Instead of following this long-accepted family tree, Matthew Baron of the University of Cambridge and his colleagues studied 74 different species, noting 457 physical characteristics and identifying 21 specific anatomical traits that categorize dinosaurs in a different way.

This is a major shake-up in the dinosaur family tree. As Ed Yong puts it in his piece published in The Atlantic, "This is like someone telling you that neither cats nor dogs are what you thought they were, and some of the animals you call 'cats' are actually dogs."

Using the 21 traits, the team created a new dinosaur family tree, placing the T. rex and other theropods with the bird-hipped ornithischians, this category now dubbed as the ornithoscelidans. Left in the saurichians category are the sauropods.

Now, both categories include carnivores and herbivores, suggesting the ancestor of all dinosaurs are likely omnivorous.

Another well-known detail about dinosaurs that the group challenged was their place of origin. While the cradle of dinosaur evolution was believed to be South America, Baron and his team said it could have been the northern hemisphere because the fossils of the oldest dinosaurs in the newly classified branches were found there, possibly in the region that is now the United Kingdom, BBC reports.