Skull anatomy of Wilson’s storm-petrel Oceanites oceanicus (Hydrobatidae, Procellariiformes)

Abstract

Oceanites oceanicus (Procellariiformes, Hydrobatidae), commonly known as Wilson’s storm-petrel, is a small seabird frequenting the South Atlantic Ocean during the austral summer. Although a number of adaptations (such as the development of salt glands, two long and tubular external nostrils, an extraordinary olfactory system, and a hooked bill covered by several horny plates) are shared with all other Procellariiformes, the ongoing discrepancy between molecular and morphological data highlights the limited osteological information available for O. oceanicus. However, we strongly believe that osteology provides significant information to understand the evolutionary history of different groups of birds. Comparative analysis of the cranium and mandible shows that adult specimens of O. oceanicus have a globose and completely fused cranium without visible sutures, and a short beak. Besides, as in other storm-petrels, the fossa glandulae nasale is interrupted by the development of the processus postocularis and the angulus postocularis; the os lacrimale develops a complex structure, with a fenestra innominata between the rostral process of the lacrimal and the os frontale; the lamina parasphenoidalis has a simpler structure with poorly defined boundaries and without processi; and the processi basipterigoidea are present.