Uma nova espécie de Tmesiphantes Simon, 1892, T. aridai sp. nov., é descrita e ilustrada baseada em três machos e três fêmeas coletadas na Floresta Nacional do Tapajós, Santarém, Estado do Pará, Brasil. Os machos distinguem se de T. perp Guadanucci & Silva, 2012 pelo aspecto do palpo copulador com uma projeção tegular basal inconspícua, apresentando um êmbolo muito delgado, com quilhas mais curtas, não se estendendo até o ápice, e distinguem se de T. nubilus Simon, 1892 pela apófise tibial com dois ramos de tamanho semelhante, o prolateral com um forte espinho na margem retrolateral. As fêmeas se assemelham a T. nubilus pelo aspecto dos receptáculos seminais, porém com uma constrição menos evidente e formato do ápice irregular. A nova espécie representa o primeiro registro de Tmesiphantes para a região amazônica, elevando para oito o número de espécies conhecidas.

A new species of Tmesiphantes Simon, 1892, T. aridai sp. nov., is described and illustrated based on three males and three females collected at the Floresta Nacional do Tapajós, Santarém, state of Pará, Brazil. Males can be distinguished from T. perp Guadanucci & Silva, 2012 by the palpal bulb with an inconspicous tegular basal projection, but presenting a very slender embolus with shorter keels not extending to the tip, and from T. nubilus Simon, 1892 by the tibial apophysis with two similarly sized branches, the prolateral one with a strong spine on the retrolateral margin. Females resemble T. nubilus by the aspect of the seminal receptacle but the constriction near the apex is less evident and apex shape is irregular. The new species represents the first record of Tmesiphantes from the Amazonian region, bringing the total number of species to eight.

Acanthoscurria natalensis Chamberlin, 1917 is redescribed. The following species are considered junior synonyms of A. natalensis: A. cursor Chamberlin, 1917, A. fracta Chamberlin, 1917, A. rondoniae Mello-Leitão, 1923, A. chiracantha Mello-Leitão, 1923, and A. parahybana Mello-Leitão, 1926. All examined specimens, including the types, share the same general aspect, morphology of the sexual organs, color, and measurements. Acanthoscurria natalensis resembles A. paulensis Mello-Leitão, 1923 and A. chacoana Brèthes, 1909 in the general aspect, size, and by the morphology of the sexual organs: male palpal bulb with embolus ending like a shell, due to the prolateral and superior keels. It can be distinguished from these two species by the less developed keels and the longer embolus. The female resembles A. paulensis and A. chacoana by the fused base of the spermathecae and differs by the more evident lobes, projected from base. The distribution of A. natalensis is expanded to Brazilian states covering the Caatinga and the Cerrado biomes

The male of Acanthoscurria paulensis Mello-Leitão, 1923 is redescribed and the female is described for the first time. The male holotype, from Pirassununga, state of São Paulo, Brazil, could not be located and the redescription is based on specimens collected in the type locality. Acanthoscurria atrox Vellard, 1924 is considered a junior synonym of A. paulensis based on their original descriptions and figures of the male palpal bulb, and also supported by the study of several specimens from both type localities, Pirassununga and Campo Grande, state of Mato Grosso do Sul, Brazil. Acanthoscurria guaxupe Piza, 1972 is also considered a junior synonym of A. paulensis based on examination of the holotype. Acanthoscurria paulensis resembles A. chacoana Brèthes, 1909, A. juruenicola Mello-Leitão, 1923, and A. geniculata (C.L. Koch, 1842) by the large size (over 50 mm). The male of A. paulensis resembles that of A. chacoana,A. juruenicola, and A. geniculata by the aspect of the palpal bulb with an embolus ending like a shell, due to the well-developed prolateral inferior and superior keels. It can be distinguished from A. chacoana by the palpal bulb less compact and with a longer embolus and from A. juruenicola and A.geniculata by the absence of a third accessory keel. The female resembles A. chacoana,A. juruenicola, and A. geniculata by the fused base of the spermathecae, and differs by the square or slightly wider than longer base of the spermathecae and by the terminal lobes directed towards each other. New distribution records for A. paulensis are provided from the Brazilian states of Mato Grosso, Goiás, Minas Gerais, Mato Grosso do Sul, Espírito Santo, Paraná, and Rio Grande do Sul.