Two new lamniform sharks (Leptostyrax stychi sp. nov. and Protolamna sarstedtensis sp. nov.) from the Early Cretaceous of NW Germany

摘要

Two new lamniform sharks, Leptostyrax stychi sp. nov. and Protolamna sarstedtensis sp. nov., based on isolated oral teeth from the Early Barremian (Early Cretaceous) of NW Germany are described. The new species are the earliest representatives of the corresponding genera, Leptostyrax and Protolamna. The validity of the genus Protolamna CAPPETTA, 1980 is confirmed, and diagnoses for both genera are amended. Teeth of Leptostyrax differ in many aspects from teeth of Protolamna including non-continuous cutting edges between main cusp and lateral cusplets, basally compressed main cusp, short root branches forming a "V", and a less developed lingual protuberance compared to teeth of Protolamna. A very remarkable difference is the lingual crown ornamentation, which is very faint and restricted to the crown base in Leptostyrax, whereas it comprises long folds reaching up to the cusp tip in Protolamna. The Early Cretaceous neoselachian fauna of North Germany is characterized by several taxa exclusively known from the Early Barremian of NW Germany.