Rediscovery of an enigmatic Euro-Mediterranean Pliocene nassariid species: Nassarius crassiusculus Bellardi 1882 (Gastropoda: Nassariidae)

Nassarius crassiusculus is an enigmatic Euro-Mediterranean Pliocene nassariid. Since its description, it had not been found until recently, when new material was collected in the Pliocene of Estepona, Spain and Siena, Italy. It is a peculiar species, easily distinguished from all other fossil and modern species of the Euro-Mediterranean area. A remarkable feature is an almost complete absence of sculpture. The only other Euro-Mediterranean Pliocene and Recent nassariids without sculpture are Nassarius bonellii, Nassarius pyrenaicus and the species of Gussonea, Naytiopsis and Plicarcularia. However Nassarius crassiusculus is unlikely to be related to these species. In fact absence of sculpture in nassariine nassariids seems a derived state that possibly appeared in different lineages, some of which were already defined in the Early-Middle Miocene.