The Temnomastax genus currently has seven species described, widely distributed at the Cerrado domain in South America. In this work an eighth species, Temnomastax spielmanni sp. nov., is described from the Brazilian Amazon region. The diagnosis of this new species is based on the phallic complex characters and external morphological characteristics. Temnomastax spielmanni sp. nov. resembles Temnomastax beni Rehn & Rehn, 1942, occurring in Bolivia, but can be differentiated by some external characters. The phallic complex of T. spielmanni sp. nov. presents characters not yet known in Temnomastacinae; this fact reinforces the need for a revision of this subfamily, which may clarify the existing phylogenetic relationships.
Phallic complex; external morphology; distribution
