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

The early Oligocene (Rupelian) sirenian Halitherium schinzii Kaup, 1838 represents the type species of the genus Halitherium Kaup, 1838 and it 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 of H. schinzii Kaup, 1838, the new genus and species Kaupitherium gruelli are established on the basis of a nearly complete holotype. The second taxon resembles K. gruelli 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 synonymised under “H. schinzii” is re-validated as the holotype of K. bronni (Krauss, 1858). On the basis of palaeoecological 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”.

渐新世早期（吕珀尔阶，Rupelian）的海牛类（sirenian）物种辛氏海牛兽（Halitherium schinzii Kaup, 1838）为海牛兽属（Halitherium Kaup, 1838）的模式种。本文基于原本归入该类群的骨骼材料的形态学重新评估，对其展开系统修订。本研究为该类群的颅骨与颅后解剖结构提供了全新且全面的研究数据，并明确区分了两种同域分布的物种。遵循近期关于辛氏海牛兽（Halitherium schinzii Kaup, 1838）无效且应被废弃的研究结论，本文依托一件近乎完整的正模标本，建立了新属新种格鲁埃尔考皮海牛兽（Kaupitherium gruelli）。第二类群在诸多骨骼特征上与格鲁埃尔考皮海牛兽高度相似，例如鼻骨退化且无犬齿，但主要凭借后犬齿段的齿式以及枕上骨形态得以明确区分。此前被归入“辛氏海牛兽”的一件具有鉴定诊断意义的头骨顶盖标本，被重新确立为布氏考皮海牛兽（Kaupitherium bronni (Krauss, 1858)）的正模标本。基于古生态学相关启示，本文提出假说以解释两个类群的地层分布重叠与生物地理分布重叠现象，即二者的同域共存特征。本次修订补充了诊断特征与最新的同物异名列表，完善了分类学相关信息。对“辛氏海牛兽”的系统修订为既往海牛类的物种多样性研究提供了全新数据，同时也为原本归入“海牛兽属”的物种开展分类学与系统学重新评估奠定了坚实基础。