[2] Females are distinguished from other three-clawed Stenoterommata by their spermathecae, which have a short basal portion and a single receptaculum arising from near the tip of the base.

Males are diagnosed by one of the species autapomorphies: the presence of numerous short spines on the ventral metatarsus I. Entre Ríos and northern Buenos Aires Province.

S. tenuistyla lives in short, branched burrows, lined with a dense layer of silk.

In Buenos Aires they have been found in the banks of the Rio Parana, along a stretch of 50 km; north of there, they appear to be replaced by S. crassistyla.

During daytime, the burrows had their entrances closed with silk and debris and were not directly visible.