Osteological descriptions of steno bredanensis in the Canary Islands

Abstract

In the Canary archipelago, 30 species of cetaceans have been recorded in its waters, 27 of which have one or some stranding records since the 1980s to date. One of these, the “rough-toothed dolphin” Steno bredanensis, is globally poorly known and there are few data on the osteology of this species from a few regions. Here we present the first osteological study of Steno bredanensis from the Canary Islands to increase the nowledge about the taxonomy and adaptations of the species. We carried out steological analyses of different bones of 27 specimens stranded in the Canary Islands, including 17 complete skeletons. The results were compared within each other and by sex, as well as with other cetacean species, mainly Delphinidae species present in the archipelago. The skeletal ontogeny was analyzed in specimens with a total length between 82cm and 236cm., contrasting the fusion degree of the various cranial sutures and the synostosis of the vertebral complex, the sternum, the hyoid and the proximal pectoral region. An adult female was studied separately as it presented a different axial skeleton to the rest of the analyzed specimens as well as to the published data from other regions, highlighting a significantly higher number of vertebrae, and a sternum resembling other delphinids. The results of the studied specimens suggest the presence in the Canary Islands of two forms, one smaller, as well as sexual dimorphism identified in some metric variables of the skull. All studied animals presented dental furrows characteristic of the species, regardless the stage of development. This study contributes to implement the current knowledge of Steno bredanensis.