Material obtained from recent collections was used to revise taxonomy of the genus Atlantirivulus in the coastal basins of south – eastern Brazil, making possible to recognise four new species: Atlantirivulus maricensis, new species, from the rivers drainages connected to the Maricá lagoon system; Atlantirivulus guanabarensis, new species, from river drainages flowing into the Guanabara bay; Atlantirivulus paranaguensis, new species, from the river basins of the plain area adjacent to the Paranaguá bay; and Atlantirivulus ribeirensis, new species, from the Ribeira de Iguape river basin. All the new species herein described are members of the A. santensis species group, diagnosed by the lateral line being divided in two sections. Atlantirivulus maricensis is considered to be closely related to A. janeiroensis, A. jurubatibensis and A. nudiventris by all sharing a horizontally elongated female caudal spot, whereas A. guanabarensis seems to be more closely related to A. lazzarotoi and A. simplicis, by all having a high number of neuromasts in the section of infraorbital series around orbit, and A. paranaguensis seems to be more closely related to A. santensis by both having the anal and caudal fin margin highly black pigmented in males; relationships of A. ribeirensis among congeners is unclear, but the presence of intense yellow pigmentation on venter suggests close relationships with A. santensis. Characters used to diagnose new species include colour patterns, number of scales in the longitudinal series and vertebrae, and shape of caudal fin.

Atlantic Forest, Biodiversity, Killifish, Systematics, Taxonomy