A new species of Branchamphinome (Annelida: Amphinomidae) from the South-western Atlantic, with an emendation of the genus

The genus Branchamphinome Hartman, 1967 is a moderately understood genus of Amphinomidae that differs morphologically from most other genera in the form of its chevron-shaped caruncle and the presence of branchiae from chaetiger 1. Branchamphinome is presently represented by two deep-water species: B. antarctica, described from the Southern Ocean and B. islandica, from Iceland. We describe a new species of Branchamphinome from shallow South-west Atlantic waters, coast of Brazil. The new taxon revealed the surprising presence of notopodial hooks in chaetiger 1, which was subsequently also found to be present in the lectotype of B. antarctica. Both the genus and Hartman's species are emended to include this morphological feature. Historically, the presence of notopodial hooks has long been considered a diagnostic character for the genus Paramphinome, particularly when distinguishing Paramphinome from Linopherus. Branchamphinome tropicalis sp. nov. was found inhabiting sand sediments at depths of 150 m and temperatures of 16–20°C. Branchamphinome tropicalis sp. nov. differs from its congeners by its characteristic and highly developed pigmentation pattern, shape of the caruncle, branchiae and disposition of prostomial eyes. This is the first report of this genus from shallow tropical waters.