Systematic revision of the genusScaphander(Gastropoda, Cephalaspidea) in the Atlantic Ocean, with a molecular phylogenetic hypothesis

Abstract

The genus Scaphander (Gastropoda, Cephalaspidea) is a group of predominantly deep-sea, soft-bottom snails with extant species distributed worldwide from the Arctic to the Antarctic. There are approximately 45 species described worldwide, of which about 18 are considered to be valid. The systematics of Scaphander has traditionally been shell-based, but shell characters often show high intraspecific variability, and this led to a high number of nominal names available of unclear taxonomic status. The main objectives of this article are to revise the systematics of the Atlantic species of Scaphander, and to produce an identification key and a molecular phylogeny to aid with species delimitation. The validity of species was assessed following an integrative approach combining the study of type material and original descriptions, shells, morpho-anatomical characters, and molecular phylogenetics. Anatomical structures were documented by drawings, macro-photography, and scanning electron microscopy (SEM). Two mitochondrial (COI and 16S rRNA) and one nuclear (28S rRNA) genes were sequenced, and Bayesian molecular phylogenetic hypotheses were produced. Representatives of the Cephalaspidean genera Bulla and Haminoea were included to test the monophyly of Scaphander. Eight species of Scaphander were recognized in the Atlantic Ocean. Three species are restricted to the western Atlantic (Scaphander clavus, Scaphander darius, and Scaphander watsoni), one is distributed only in the eastern Atlantic (Scaphander lignarius), one is endemic to the Azores (Scaphander gracilis; this species is only known from shells), and three have amphi-Atlantic distributions (Scaphander bathymophilus, Scaphander nobilis, and Scaphander punctostriatus). Shell characters and the morphology of the male reproductive system were found to be the best diagnostic characters for species recognition. The molecular phylogeny confirms the monophyly of Scaphander, and is largely congruent with species delimitation based on morpho-anatomical characters. © 2013 The Linnean Society of London