The new sp. (holotype S: Diamantino, state of Mato Grosso, IV-1988; deposited in the author’s collection) is described and illustrated. It shares with A. furcatus the presence of a pair of long spines on the rear of the occiput but differs from it by the color pattern, shape of the vulvar lamina and mainly by a pair of hook-like prominences on the superior margin of the occipital foramen.