Identity and phylogeny of the late Paleozoic Subulitoidea (Gastropoda)

The Subulitoidea have long been an enigmatic group of Paleozoic gastropods and share many characters of post-Paleozoic clades. Newly described protoconchs from several late Paleozoic subulitoid species have been employed in a phylogenetic analysis of the group. Late Paleozoic representatives, the Soleniscidae, are caenogastropods with an unornamented orthostrophic larval shell. The Meekospiridae have a smooth blunt protoconch of about two whorls. In contrast to previous interpretations, this protoconch is not heterostrophic or heterostrophy is not obvious. Therefore, a placement of the Meekospiridae with the genus Girtyspira in the Opisthobranchia is to be treated with caution. The new lanthinopsis -like genus Imogloba has a gobular subulitid-like teleoconch but its protoconch consists of a smooth first whorl which is loosely coiled and a larval shell with a characteristic non collabral ornament. Therefore, a close relationship between Soleniscidae and Imogloba is unlikely and the new family Imoglobidae is proposed. We found no clearly heterostrophic groups within the late Paleozoic subulitoid gastropods. The phylogenetic analysis of all subulitoid genera with known protoconchs provides little support for the monophyly of the Subulitoidea, particularly for a close relation between the Meekospiridae and the Soleniscidae. However, the Soleniscidae and Meekospiridae are probably monophyletic groups. Most genera are restricted to the Paleozoic, although several Mesozoic genera may hold descendants of Paleozoic Subulitoidea. Finally, a hypothesized link between Subulitoidea and Neogastropoda based on the presence of an anterior notch in both groups is unlikely.