A mummified duck-billed dinosaur with a soft tissue cock’s comb.

Among living vertebrates, soft-tissues are responsible for labile appendages (combs, wattles, proboscides) that are critical for activities ranging from locomotion to sexual display [1]. However, soft tissues rarely fossilise and such soft-tissue appendages are unknown for many extinct taxa, including dinosaurs. We report a remarkable ‘mummified’ specimen of the hadrosaurid dinosaur Edmontosaurus regalis from the latest Cretaceous Wapiti Formation, Alberta, Canada, which preserves a three-dimensional cranial crest (or ‘comb’) composed entirely of soft tissue. Previously, crest function has centred on the hypertrophied nasal passages of lambeosaurine hadrosaurids, which acted as resonance chambers during vocalization [2–4]. The fleshy comb in Edmontosaurus necessitates an alternative explanation most likely related to either social signalling or sexual selection [5–7]. This discovery provides the first view of bizarre, soft-tissue signalling structures in a dinosaur and provides additional evidence for social behaviour. Crest evolution within Hadrosaurinae apparently culminated in the secondary loss of the bony crest at the terminal Cretaceous; however, the new specimen indicates that cranial ornamentation was in fact not lost but substituted in Edmontosaurus by a fleshy display structure. It also implies visual display played a key role in the evolution of hadrosaurine crests and raises the possibility of similar soft-tissue structures among other dinosaurs.