The taxonomy of flabelligerid polychaetes has been mainly based on chaetal features; however, some confusion has occurred due to the lack of standardization of their shapes. Therochaeta Chamberlin, 1919 was proposed for Stylarioides collarifer Ehlers, 1887 because it has pseudocompound neurohooks and a collar-shaped anterior shield made of cemented sediment particles. The shield is made of particles of varying size and extends along the first three-two chaetigers, usually covering them completely. There are some species described as closely allied toTherochaeta collarifera (Ehlers, 1887) but without pseudocompound neurohooks and less developed anterior shields. The revision of all available material has allowed the recognition of two different body patterns, especially with regard to the type of neurochaetae present in some anterior chaetigers. As a result, Therochaeta is restricted and a new genus, Paratherochaeta n. gen., is herein proposed. Therochaeta includes four species besides the type species: Therochaeta caudata (Rioja, 1963) n. comb. and Therochaeta pacifica Fauchald, 1972 from the Eastern Pacific Ocean, Therochaeta fauchaldi n. sp. from the Gulf of Mexico, Therochaeta flabellata (Sars in Sars, 1872) from the Norwegian Sea, from the Eastern Pacific Ocean. Paratherochaeta n. gen., with Therochaeta antoni Kirkegaard, 1996 from the Bay of Bengal, Indian Ocean as the type species, includes seven other species: Paratherochaeta africana (Rullier, 1965) n. comb., n. stat., Paratherochaeta augeneri n. sp. and Paratherochaeta scutigeroides (Augener, 1918) n. comb. from Western Africa, Paratherochaeta coronata (Ehlers, 1908) n. comb. from the Western Indian Ocean, Paratherochaeta ehlersi n. sp. from the Southwestern Indian Ocean, Paratherochaeta orensanzi n. sp. from the Southwestern Atlantic Ocean, Paratherochaeta scutigera (Ehlers, 1887) n. comb. from the Grand Caribbean Sea.
Stylarioides, Pherusa, Semiodera, pseudocompound neurohooks, anterior shield, new combinations, new status, new genus, new species.