The dinobird Caudipteryx

The dinobirds are feathered dinosaurs. Not feathers for flight like Archaeopteryx, but feathery coverings for insulation and decoration. They confirm John Ostrom's theory that birds are the descendants of predatory dinosaurs – the theropods.

To understand how scientists reached this conclusion, it helps to sort theropod dinosaurs into groups, using features that are easy to see. Features that are shared by all members of the group tend to be oldest. As members of the group evolved and changed, so new features appeared. Some features, such as the reduced hands and extremely short arms shown by Tyrannosaurus rex, were an evolutionary dead end. Other features, such as very long hands, gave a real advantage to a whole set of animals whose descendants are modern birds.

When the dinobirds were found and their bones examined, scientists faced two challenges. First, they had to confront a former scientific 'truth' that only birds had feathers – as these dinosaurs definitely had feathers and certainly were not birds. Secondly, they hadto fit each dinobird into its theropod dinosaur set.

Table showing relationships between dinobirds and other dinosaurs.