Abstract
A new species of Trichomycterus is described from rocky and psammic sectors near the main channel of the middle and upper Rio Doce basin in Southeastern Brazil. Trichomycterus astromycterus n. sp., is distinguished from all congeners by a number of autapomorphic characters, such as the distally expanded maxilla; the short and thick mesethmoid cornua; and the elongated anterior process of the vomer. Additional characters (short barbels, large head, 33 vertebrae, ii+8 or ii+9 dorsal‐fin rays, nine dorsal‐fin pterygiophores, markedly enlarged lips, narrow caudal peduncle, bilobed caudal fin with the lower lobe longer than the upper one) also distinguish the new species from all its congeners in Southeastern Brazil and from most congeners anywhere. Examination of internal anatomy reveals that T. astromycterus shares some intriguing characteristics with the austral genus Bullockia Arratia et al ., 1978. However, the phylogenetic significance of such similarities is still uncertain and will require further comparative study. For this reason, the new species is provisionally included in the all‐encompassing genus Trichomycterus . An osteological description is presented on the basis of CT‐scan imaging and cleared and stained specimens.