Spiny Crab Spiders

Spinaarachne Machado, 2025

Type species: Stephanopis hirsuta L. Koch, 1874

Fauna Portal Genus Number: 3721

(after Machado and Teixeira 2025): The genus Spinaarachne esembles Heriaeus and Epicadinus by its component species presenting a “spiny/hairy” appearance, due to the presence of long and needle-shaped setae covering their entire bodies. At first sight, Spinaarachne can be distinguished from these genera by its square-ended, and sometimes bifid, opisthosoma. In Heriaeus, the spiders present rounded abdomen, while Epicadinus is recognizable by its pair of lateral abdominal projections and a median-posterior one, which is projected upwards. The male genitalia have similarities to those of some Stephanopis species in bearing a forked retrolateral tibial apophysis (RTAdbr + RTAvbr), a paracymbium and the whip-like embolus. However, in Spinaarachne, the embolus is longer, and accommodated on a ventral tegular ridge, instead of being on the apical portion of the tegulum; the paracymbium is rounded and wide, while in males of Stephanopis this structure is acute and curved. While in Stephanopis both branches of the retrolateral tibial apophysis are acute and similar in size, in Spinaarachne the RTAvbr is longer than the RTAdbr and spoon-shaped, with a blunt tip. Females have a flat epigynal plate with depressed atrium and an anterior fold forming a weakly developed hood. The copulatory openings in Spinaarachne are slit-shaped like in Stephanopis, but covered by bulged lobes instead of being totally exposed; in internal dorsal view, the females of Spinaarachne are unique and distinguishable by their ribbon-like copulatory ducts leading to a coiled tubular pair of spermathecae, resembling intestine loops, each with a porous glandularhead.