Notes on the evolution and higher classification of the subclass Neritimorpha (Gastropoda) with the description of some new taxa

Neritimorpha represent a subclass of the Gastropoda that regarding its anatomy is close to the Archaeogastropoda, regarding its ontogeny it resembles more the Caenogastropoda. Ontogenetic development includes a larval phase during which a planktotrophic veliger may produce a larval shell. The members of the new order Cycloneritimorpha have a larval shell that is tightly coiled and rounded. The representatives of the other new order Cyrtoneritimorpha have a hook-like openly coiled protoconch. Recognition of these two new taxa splits seemingly well established Palaeozoic gastropod groups like the Platyceratoidea which apparently are polyphyletic. The protoconch shape is evidence for teleoconch convergence between a Carboniferous Orthonychia and the Triassic Pseudorthonychia n. gen. Neritimorpha existed from Ordovician onward first with the Cyrtoneritimorpha and later the still extant Cycloneritimorpha with an overlap in time of occurrence from the Devonian to the Permian.