New specimen of Archaeopteryx provides insights into the evolution of pennaceous feathers

A new specimen of Archaeopteryx with extensive pennaceous feather preservation. Feathers prominent on latest Archaeopteryx fossil The discovery of numerous feathered dinosaurs and early birds has set the iconic 'Urvogel' (or 'first bird') Archaeopteryx in a broader context. But this venerable taxon still has the capacity to surprise. A newly discovered specimen from the Solnhofen limestone in Bavaria — only the eleventh since 1861 — shows a generous covering of feathers all over the body. Of particular note is a hindlimb covering resembling feathered 'trousers'. Analysis of feather distribution on the limbs and tail strongly suggests that pennaceous feathers — the type we are familiar with on birds today — evolved for reasons other than flight, perhaps for display. Discoveries of bird-like theropod dinosaurs and basal avialans in recent decades have helped to put the iconic ‘Urvogel’ Archaeopteryx 1 into context 2 , 3 , 4 , 5 , 6 and have yielded important new data on the origin and early evolution of feathers 7 . However, the biological context under which pennaceous feathers evolved is still debated. Here we describe a new specimen of Archaeopteryx with extensive feather preservation, not only on the wings and tail, but also on the body and legs. The new specimen shows that the entire body was covered in pennaceous feathers, and that the hindlimbs had long, symmetrical feathers along the tibiotarsus but short feathers on the tarsometatarsus. Furthermore, the wing plumage demonstrates that several recent interpretations 8 , 9 are problematic. An analysis of the phylogenetic distribution of pennaceous feathers on the tail, hindlimb and arms of advanced maniraptorans and basal avialans strongly indicates that these structures evolved in a functional context other than flight, most probably in relation to display, as suggested by some previous studies 10 , 11 , 12 . Pennaceous feathers thus represented an exaptation and were later, in several lineages and following different patterns, recruited for aerodynamic functions. This indicates that the origin of flight in avialans was more complex than previously thought and might have involved several convergent achievements of aerial abilities.