The Miocene genus Mantellina (Bivalvia: Limidae) discovered living on the deep reefs off Curaçao, with the description of a new species

Abstract

Mantellina translucens n. sp. inhabits the deep reefs (215-310 m) off southeastern Curaçao, occurring singly or in pairs, attached to vertical rock walls and boulders by thin byssal threads. This species differs from all living Limidae in having an exceptionally thin, comarginally corrugated shell that is longer than tall and lacks radial sculpture. This new species possesses a unique suite of characters associated with adaptations to an epibyssate mode of life in bathyal habitats, including simplification of the digestive tract, possibly indicating omnivory. It is assigned to the genus Mantellina Sacco, 1904, previously known only from fossil deposits of Burdigalian to Serravallian Miocene age of the Central Paratethys, on the basis of similar shell morphology. Anatomical characters and ribosomal DNA sequence data (18S and 16S genes) confirm placement of this taxon within the family Limidae, yet its shell superficially resembles those of several genera of the extinct family Inoceramidae, while differing in hinge morphology and shell ultrastructure. A preliminary molecular phylogeny recovered Limidae as a monophyletic clade within Pteriomorphia, with Mantellina derived relative to Limaria, and sister group to a clade containing the remaining representatives of Limidae. Ctenoides was not monophyletic. The phylogenetic tree based on molecular data does not support previously proposed suprageneric relationships based on morphological data.