Non-metric characters in two species of Sotalia (Gray, 1866) (Cetacea, Delphinidae)

Abstract

Analyses of non-metric characters of the skull and cervical vertebrae were performed among samples of dolphins of the genus Sotalia from the north, northeast and south Brazilian coast (S. guianensis) and also samples from the Amazon River Basin (S. fluviatilis) as part of an osteological descriptive study. The results demonstrated that there was a higher percentage of occurrence of fenestrae in the occipital region (66%) and cervical ribs in the cervical vertebrae (87%) in the riverine species. The vomer in wide shape was more frequent in the riverine species (57%), followed by the intermediate (32%) and narrow shape (11%), that was found to be more frequent in the marine species (66 to 76%). In relation to the lacerate anterior foramen, it was observed that an open/elongated shape is more common in the riverine species (88%). Most samples in the marine species present this foramen divided by a spike shaped projection (72 to 98%). The ventrally visible location of the hypoglossal foramen was more often observed externally displaced in S. guianensis (88 to 98%), while in S. fluviatilis, most samples (87%) presented this foramen internally displaced to the jugular notch, and not visible in ventral view. The fluvial species seems to present neoteny (or maintenance of juvenile characters in adults) in relation to the position of the pterygoids and in development of lacerate anterior foramen.