First Report of a Hollow Cranial Crest in an Early-Diverging Duck-Billed Dinosaur, with Implications for Convergent Evolution of Acoustic Signaling

Cranial crests have evolved multiple times in the evolutionary history of vertebrates, serving primarily for visual display. In duck-billed lambeosaurines, one of the most successful dinosaur clades of the Late Cretaceous, the cranial crest became hollow along the paired premaxillae and nasals, and was secondarily selected as a resonating structure atop the skull roof, facilitating acoustic signaling. Here we report the first instance of a hollow supracranial crest in a non-lambeosaurine ornithopod dinosaur, the early-branching hadrosauroid Qianjiangsaurus changshengi, where the paired accessory endonasal cavities just above the nasal cavity proper occur following the dorsoventral thickening of the nasals. This novel nasal cavity configuration is associated with the helmet-like hollow supracranial crest solely formed by the nasals. Comparative resonance modeling suggests that the nasal cavity of Q. changshengi could amplify low-frequency vocalizations similar to those of late-branching lambeosaurines. Seven analogous skull features (including the hollow supracranial crest) and similar low-frequency acoustic capabilities of nasal cavities between Q. changshengi and late-branching lambeosaurines reveal a striking morphological and functional convergence that would likely facilitate safer, more efficient social communication among hadrosauroids. This convergence can be explained by adaptive evolution under similar selection pressures, combined with developmental constraints due to gene pleiotropy.