Distribution and comments on the morphology of Centroscymnus owstonii Garman, 1906 (Squaliformes: Somniosidae), with focus on its occurrence in the Indian Ocean

The Roughskin Dogfish Centroscymnus owstonii is one of the most widespread deepwater shark species, but its global distribution is mostly based on patchy records. In this study, C. owstonii was reinvestigated with focus on its poorly known distribution in the western and eastern Indian Ocean. Previous records of the species from the Seychelles, which, for decades, were considered to be of a different species, were verified in this study. Furthermore, the first records from off Reunion Island, Madagascar, and Indonesia are provided, including the smallest free-swimming specimen of the species described in detail to date. Based on these specimens, a description of C. owstonii is given with updated and extended morphometric data, photographic documentation and scanning electron microscopy (SEM) images of dermal denticles. Additionally, specimens from the Indian Ocean are compared with specimens from the Pacific and Atlantic Oceans. For the Pacific Ocean, the first record from the central western North Pacific is provided from the Hawaiian-Emperor seamount chain. This record also represents the most open ocean known occurrence of C. owstonii.