Evidence for two sympatric sirenian species (Mammalia, Tethytheria) in the early Oligocene of Central Europe

Abstract

AbstractThe early Oligocene (Rupelian) sirenianHalitherium schinziiKaup, 1838, which represents the type species of the genusHalitheriumKaup, 1838, is revised herein based on a morphological re-evaluation of skeletal material originally assigned to this taxon. This study provides new and comprehensive information on the cranial and postcranial anatomy and allows the distinction of two sympatric species. Following a recent approach on the invalidity and subsequent rejection ofH.schinziiKaup, 1838,Kaupitherium gruellinew genus new species is established on the basis of a nearly complete holotype. The second taxon resemblesK.gruellin. sp. in a number of skeletal features, such as reduced nasals and absence of the canines, but can be clearly distinguished mainly by the post-canine dental formula and the supraoccipital morphology. The diagnostic skullcap of a species formerly synonymized under “H.schinzii” is re-validated as the holotype ofK.bronni(Krauss, 1858). On the basis of paleoecological implications, a hypothesis is established to explain the overlapping stratigraphic and biogeographic occurrences (i.e., sympatry of both taxa). A diagnosis and up-to-date synonymy complement the taxonomical information. The revision of “H.schinzii” provides new data on the past sirenian diversity and forms the basis for a taxonomic and systematic re-evaluation of species originally grouped in the genus “Halitherium.”