The new genus Yanomamius n. gen. from Brazilian and Venezuelan Amazon is described, with three new species from Brazil: Y. franciscoi n. sp. (type species), Y. raonii n. sp., and Y. neblina n. sp. The enigmatic Venezuelan species described as Holothele waikoshiemi Bertani Araújo, 2006 and presently included in Guyruita Guadanucci et al. (2007) is transferred to the new genus, making the new combination Y. waikoshiemi (Bertani Araújo, 2006) n. comb. Yanomamius n. gen. is closely related with the schismatotheline genera Schismatothele Karsch, 1879 and Euthycaelus Simon, 1889 sharing as probable synapomorphies a group of short spines on the retrolateral distal tibia of male palp and the shape of bulb. They differ by the position of the spines in a compact group instead of in rows and by a tapering embolus. Females differ from Schismatothele and Euthycaelus by the spermathecae weakly sclerotized. A series of recent phylogenies based on molecular data suggested a close relationship between schimatothelines and psalmopoeines. The male tibia I of Yanomamius n. gen. species have a series of ridges or a single protuberance behind the tibial apophyses that resemble those of psalmopoeines and strengthen the idea of close relationship of the two subfamilies.
Keywords: Araneae, Amazon rainforest, biodiversity, Psalmopoeinae, Schismatothelinae, Taxonomy.