Two new pleurotomariid (Gastropoda) species, including the largest Bathrotomaria, from the Berriasian (Early Cretaceous) of Kutch, western India

The Mesozoic pleurotomariids have a wide biogeographic distribution in shallow seas. Cenozoic pleurotomariids, however, are biogeographically more restricted and are occupants of deep-sea rocky substrates. This radical ecological shift is also reflected in shell morphology and the Mesozoic and Cenozoic forms have long been recognized as different genera. Attempts to synonymize the Tertiary and Recent forms with the Mesozoic genus Pleurotomaria Defrance, 1826 have been based on a few homeomorphic characters. Pleurotomaria sensu stricto became extinct during the Early Cretaceous. Recent molecular data are consistent with living forms belonging to a single clade, Perotrochus Fischer, 1885, with extant species having diverged after the Eocene. Hence Pleurotomaria, is re-evaluated here as an essentially Mesozoic genus and thus is disqualified from the status of a living fossil. It shows wide interspecific diversity, which has prompted workers to subdivide the genus into several subgenera. A new subgenus, Indomaria is described, its type species, P. (I.) umiensis sp. nov. being from a Lower Cretaceous deposit in western India. In addition, one new species of the related genus Bathrotomaria Cox, 1956, i.e., B. brihattama sp. nov., believed to be largest, is also described from the same horizon and locality.