Seminar

Reorganization (co-option) of pre-existing bones occur as the skeletal morphology of tetrapods evolves to produce new functions or structures. During development, evolutionary rearrangement of a given bone is limited by heterochrony and the development of neighboring bones. Cranial rearrangement was previously explored in archosaurs using Anatomical Network Analysis (AnNA) but unable to reconstruct their vast diversity, nor pinpoint these rearrangements in time. To address this, the most comprehensive dataset of archosaurs to date, including 109 species of non-archosaurian archosauriformes, pseudosuchians, Paleogene birds, and modern birds, has been compiled to constructed the topological morphospace using AnNA.

Specialization via fusion of cranial bones in archosaurs could be traced from crown archosaurs with subtle changes throughout the Mesozoic, when pseudosuchians and avemetatarsalians overlapped with non-archosaurian archosauriforms in the morphospace. The morphospace subsequently expanded with the rise of Aves, which were remarkably distinct from their predecessors. In particular, extant crocodylians were different from non-crocodylian pseudosuchians.

Additional information: Miss. Hiu Wai LEE, hiuwail@connect.hku.hk