Ascension and Saint Helena Islands are isolated volcanic islands in the South Atlantic Ocean. Records of annelids from the family Amphinomidae, commonly known as fireworms, are rare. Fireworm species recorded in both localities include Eurythoe complanata and Hermodice carunculata, which are broadly distributed throughout the Atlantic Ocean. Here we present the characterization of both species from a recent expedition to Ascension and Saint Helena. Morphologically, specimens from H. carunculata correspond to the West Atlantic population, while E. complanata specimens were clearly identified based on chaetal type. A genetic analysis, including material from Ascension and Saint Helena Islands, will be necessary to elucidate the genetic connectivity across the Atlantic Ocean.

The amphinomid polychaete Linopherus cf. canariensis was recorded for the first time in the coast of Rio de Janeiro (South-east Brazil). In 2011, a total of 15 specimens were collected in the intertidal zone of Itaipu Beach (Niterói) in dead Encope emarginata test fragments. In this study, the specimens are described, and a brief discussion about their morphological variation and invading potential is provided.

A new species of Chloeia (Annelida: Amphinomidae) is described from deep water (750–1045 m) off southern Brazil. Chloeia kudenovi sp. nov. differ from previously described species by the extremely elongated neuropodial cirri of the second chaetiger, number and position of noto- and neuroaciculae and lack of body pigmentation. This study provides additional data on the morphological diversity of the genus.

A new species of Paramphinome (Polychaeta: Amphinomidae) is described from southern Brazil (900–2000 m). Paramphinome posterobranchiata sp. nov. differs from already described species by having a small body (1–9 mm); a low number of chaetigers (10–29); branchiae in few chaetigers (0–3) and starting more posterior than in most species; and by a reduced caruncle.

Amphinomida is an ‘isolated’ clade within the polychaete group Aciculata and traditionally includes the families Amphinomidae, Archinomidae and Euphrosinidae. Archinomidae were erected for a single species, the hydrothermal vent polychaete Archinome rosacea. Originally, A. rosacea was assigned to Euphrosinidae although it shares more morphological similarities with Amphinomidae. In this study we assess the position of Archinome, Euphrosinidae and Amphinomidae by using molecular data from nuclear 18S rDNA and 28S rDNA. Parsimony, maximum likelihood and Bayesian analyses are performed on the nucleotide datasets covering in total 19 terminals from Amphinomidae, Euphrosinidae, Archinomidae and outgroups. Our results conclusively show that Euphrosinidae and Amphinomidae are sister taxa and that Archinome is sister to Chloeia within Amphinomidae. Based on these results the family name Archinomidae is treated as a junior synonym of Amphinomidae.