Cladistic analysis of the subfamily Trichobranchinae (Polychaeta: Terebellidae)

Abstract

To assess the phylogenetic interrelationships of Trichobranchinae (Polychaeta: Terebellidae), we present the results of a cladistic analysis based on morphological characters coded as contingent. We also present an alternate way to number anterior segments, based on a reinterpretation of prostomial and peristomial morphologies in different genera. The ingroup terminals included 28 species, and the outgroup included one species of Ampharetidae and four species belonging to other subfamilies of Terebellidae. The monophyly of Trichobranchinae is clearly supported by the presence of long shafted uncini in thoracic neuropodia and by the absence of ventral shields. Species of Terebellides share lamellate branchiae, uncini with a long and narrow manubrium without denticles and uncini with a long and sharp main fang in the eighth segment. Species of Octobranchus share subquadrate branchiae on segments 3, 4 and 5, notopodia first present from segment 4, and uncini with a long shafted manubrium first present from segment 6. The autapormophy for Unobranchus is the presence of a single filiform branchia on segment 3. Artacamella falls into one of the Trichobranchus clades and is treated as a junior synonym of the latter.