A new species of Paraonis and an annotated checklist of polychaetes from mangroves of the Brazilian Amazon Coast (Annelida, Paraonidae)

The polychaete fauna from the mangroves of the Amazon Coast in Maranhão state, Brazil, is reported in this study. Fourteen species are listed, namely Alittasuccinea (Leuckart, 1847); Arabella (Arabella) iricolor Montagu, 1804; Capitellacapitata (Fabricius, 1780) complex; Exogone (Exogone) breviantennata Hartmann-Schröder, 1959; Heteromastusfiliformis (Claparède, 1864); Isoldapulchella Müller, 1858; Mediomastuscaliforniensis Hartman, 1944; Namalycastisfauveli Nageswara Rao, 1981; Namalycastisgeayi (Gravier, 1901); Namalycastissenegalensis (Saint-Joseph, 1901); Nephtyssimoni Perkins, 1980; Paraonisamazonica sp. n.; Sigambrabassi (Hartman, 1945); and Sigambragrubii Müller, 1858. Among them, Namalycastisfauveli and Namalycastisgeayi are recorded for the first time in Brazil. Paraonisamazonica sp. n. is a new species for science, characterized by a rounded prostomium, 4–8 pairs of foliaceous branchiae, absent eyes, and two types of modified neurochaetae, acicular and hook-shaped.