A new troglobitic palpigrade from Central Brazil, with notes on a new opisthosomal character (Arachnida: Palpigradi).

A new species of palpigrade from the cave Gruta Cabeceira d'água in Goiás state in Central Brazil is described and illustrated based on 11 specimens: five adult males, two adult females, two immatures C and two immatures B. Eukoenenia audax sp. nov. was collected mainly in the sand banks near the main water stream, where flooding and important water fluctuations occur in the cave. The new Brazilian species shows three uncommon morphological traits: the presence of 7 + 7 setae on the propeltidium, one deuto-tritosternal seta, and 9-11 blades in the lateral organs; these characters relate Eukoenenia audax sp. nov. with only a handful of species in the world. The presence of a pair of cavities was identified in the intersegmental furrow between opisthosomal sternites III-IV, IV-V, V-VI and VI-VII. A comprehensive study of this new character was performed in other species available to the authors, and a discussion of its possible origin and function is presented.