Feather origins: taking flight back in time?

The discovery of feather-like structures in a fossil belonging to one of the two main groups of dinosaur, the Ornithischia, might date the origin of feathers back to the earliest dinosaurs as a whole — from 150 million to more than 200 million years ago. Feather-like structures of dinosaurs were thought to be restricted to a group known as theropods from the other main group of dinosaur, the Saurischia, which also includes birds.

In Nature this week, Hai-Lu You of the Chinese Academy of Geological Sciences and colleagues describe three patches of feather-like structures that are preserved in a fossil of Tianyulong confuciusi from the Yixian Formation of Liaoning in northeastern China. Tianyulong is a member of a primitive group of small bipedal ornithischians known as heterodontosaurids that is not closely related to birds, and may be the first of this group to have feather-like structures all over its body.

“The unique filaments of Tinayulong add more complexity to the issue of feather origins,” note You and colleagues. The separated structures show no signs of branching and appear to be of similar size in all patches, with the exception of longer filaments on the tail that are estimated to be up to 6 cm long.

Lawrence Witmer from the Ohio University College of Osteopathic Medicine, USA, notes in a related ‘News and Views’ article that “the ultimate question is whether the feather-like structures of Tianyulong are part of the evolutionary lineage of true feathers or an independent evolution of projecting epidermal appendages”. New fossils and new molecular and imaging techniques may help to resolve this question.