Morphology of two deep-sea Olivella from the southwestern Atlantic, with a record of a radula-less Olivellinae species (Neogastropoda: Olivoidea: Olividae)

Abstract

Two deep-sea species from southeast Brazil, originally assigned to different subgenera of Olivella, are anatomically described. Olivella (Olivina) klappenbachi and Olivella (Anasser) careorugula, both described by Absalao & Pimenta (2003), present typical Olivellinae anatomy, with internal absorption of the shell wall and a non-spiralized visceral mass, the absence of a valve of Leiblein and gland of Leiblein, and a large cuticularized and muscular stomach. Olivella klappenbachi presents the typical radular morphology of Olivellinae, while Olivella careorugula lacks a radula and odontophore, which is unique among known olivids. A well-founded phylogenetic classification of Olivella at the generic/ subgeneric level is still lacking, and the numerous proposed subgenera are mostly based on the structure of the pillar. A broader taxonomic study incorporating both morphological and molecular data is still necessary.