A new Hyphessobrycon (Characiformes: Acestrorhamphidae) of the Hyphessobrycon agulha lineage of Hyphessobryconinae from the lower Aripuanã basin, Brazil, with comments about the lineage.

A new species of Hyphessobrycon is described from a tributary of Rio Jatuarana, lower Rio Aripuanã basin, Rio Madeira basin, Apuí, Amazonas. The new species is part of the Hyphessobrycon agulha lineage, with the typical midlateral narrow black stripe immediately followed dorsally by an iridescent stripe. Its phylogenetic position is corroborated by the DNA barcoding methodology, which also indicates the new species as closely related to Hyphessobrycon ericae and Hyphessobrycon ribeiroi, with both possessing very distinct colour patterns. The new species can be distinguished from all species of Hyphessobrycon by the association of a well-defined and horizontally elongated humeral blotch with a ventral diffuse expansion, a conspicuous caudal peduncle blotch restricted to the ventral half of the caudal peduncle and proximal half of mid rays of caudal fin, the presence of a red midlateral stripe dorsal to the iridescent stripe and lateral-line scale counts.