title: Retroculus acherontos, a new species of cichlid fish (Teleostei) from the Rio Tocantins basin.
abstract: Retroculus acherontos is described from the Rio Tocantins basin, Brazil. It is distinguished from all congeners by the presence of a nuchal hump in large specimens, an irregular black blotch located on the middle of the anterior soft dorsal-fin rays, fewer pectoral-fin rays (15-16), a deeper body, a convex ventral profile, a more transversely convex ventral surface of the body, and by chest scales similar in size to the scales on the side. An expanded diagnosis for the genus Retroculus is provided.
authors.affiliation: Museu de Zoologia da Universidade de São Paulo, Caixa Postal 42494, 04218-970, São Paulo, SP, Brazil.; Email: milandim@usp.br.
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Landim
authors.affiliation: Museu Nacional/Universidade Federal do Rio de Janeiro, Setor de Ictiologia, Departamento de Vertebrados, Quinta da Boa Vista s/n, 20940-040, Rio de Janeiro, RJ, Brazil.; Email: moreira.c.r@gmail.com.
authors.forename: Cristiano R
authors.initials: CR
authors.lastname: Moreira
authors.affiliation: Universidade Federal do Estado do Rio de Janeiro, Instituto de Biociências, Departamento de Ciências do Ambiente. Av. Pasteur, 458/sala 512F, 22290-240, Rio de Janeiro, RJ, Brazil; Email: carlos.figueiredo@gmail.com.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Figueiredo
mesh_terms: D063147:Animal Distribution; D000825:Animal Structures / Q000033:anatomy & histology / Q000254:growth & development; D000818:Animals; D049628:Body Size; D001938:Brazil; D023681:Cichlids / Q000033:anatomy & histology / Q000145:classification* / Q000254:growth & development; D017753:Ecosystem; D005260:Female; D008297:Male; D009929:Organ Size