Spirobranchus Blainville, 1818

Brandão, Ivison Cordeiro & Brasil, Ana Claudia dos Santos, 2020, On a new species of Spirobranchus Blainville, 1818 (Annelida: Serpulidae) and considerations on the genus along the Brazilian coast, Papéis Avulsos de Zoologia 60, pp. 1-17 : 3

Genus Spirobranchus Blainville, 1818

Type-species: Spirobranchus giganteus ( Pallas, 1766) .

Diagnosis (expanded from ten Hove & Kupriyanova, 2009): Tube circular to triangular in cross section, one to five longitudinal keels present, the dorsalmost possibly forming a pointed or flat anterior projection; alveoli and/ or transverse ridges possibly present. Radioles arranged in spirals (1 to 8 whorls) in larger species and semicircles in smaller species. Inter-radiolar membrane present. Radiolar photoreceptors absent or various types: simple ocelli, paired or individual ocellar clusters, depending on the taxon. Mouth palps present. Peduncle generally broader than radioles, triangular in cross-section, with distal wing-like projections; constriction between peduncle and opercular ampulla may be present; peduncle inserted left to midline of prostomium. Operculum composed of a basal ampulla as inverted or flattened cone; calcareous reinforcement forming a flattened endplate, thorns may be present. Simple ocelli possibly present in the basal ampulla. Thorax formed by collar and six posterior segments. Collar tri-lobate, chaetigerous or, possibly, achaetous. Tonguelets present between the dorso-lateral lobes and the mid-ventral lobe. Thoracic membrane continuous with dorso-lateral lobes extending throughout the thorax and forming ventral apron over anterior abdominal region. Spirobranchus collar chaetae and/or limbates. Limbate thoracic notochaeta; Saw-shaped thoracic uncini (rasp-shaped in some taxa), anterior main peg bent downwards, gouged. Thoracic tori ending ventrally apart in anterior region and closer in posterior region, forming a ventral thoracic triangular depression. Abdominal uncini similar to thoracic ones. True trumpet-shaped abdominal neurochaetae, distally bent, with 2 distal rows of denticles and a pointed lateral process. Progressively longer neurochaetae along abdomen. Ventral glandular shields present.