Die systematische Stellung der Euomphalidae (Gastropoda)

Abstract

The core group of Euomphalidae with the generaEuomphalus, Straparollus, Serpulospira, Phymatifer, Schizostoma, Nodeuomphalus n. g. (Devonian to Permian) are characterized by a cyrtoconic, openly coiled, planispiral protoconch. This character distinguishes them from members of the four extant subclasses of the Gastropoda (Archaeogastropoda, Neritimorpha, Caenogastropoda and Heterostropha) and places the Euomphaloidea at a similarly high taxonomic level, the new subclass Euomphalomorpha. WithEuomphalopsis the group may have made its first appearance in the Late Cambrian, and it is certainly present from the Mid Devonian to Late Permian and thus the range is about 300 million years in duration. Throughout the existence of the Euomphaloidea other gastropod units developed convergent shell forms which can be detected by the morphology of the protoconch and, in well preserved fossils, the mineralogical and structural composition of the shell. The new taxa Euomphalomorpha n. subclassis,Nodeuomphalus n. g.,N. paffrathianus n. sp., and“Planerotinus” scheeri n. sp. are described.