The latest revision involving the genus seems to be that of Goloboff (1995).
His diagnosis for Acanthogonatus pissii (note spelling):
"This species is unmistakable because of its coloration, with a reddish cephalothorax and a dark abdomen with yellowish oblique stripes, with dark legs and palps. The tip of the male embolus is widened (fig. 86B), unlike that of other species in the genus; the female spermathecae are most similar to those of the Uruguayan A. tacuariensis, and vaguely similar to those of A. huaquen and A. quilocura (which differ in their coloration)."
He treats A. francki (note spelling, misspelled by Goloboff) and two other species forming a "species group" within the genus Acanthogonatus. These differ from the rest of species of the genus including A. pissii:
"This species group is characterized by the presence of 1-1-1 prolateral spines on patella IV, the loss of the spur on the male tibia I (a reversal, also occurring, in parallel, in A. fuegianus), and the more coniform male bulb."
Goloboff, P. A. 1995. A revision of the South American spiders of the family Nemesiidae (Araneae, Mygalomorphae). Part I: species from Peru, Chile, Argentina, and Uruguay. Bulletin of the American Museum of Natural History224: 1-189. Online at http://hdl.handle.net/2246/1624
Bumping because this is like the only info i can find anywhere about them. I recieved some Acanthoganatus unexpectedly among some other spiders. The seller had no idea what they are and they werent labelled. They're pretty uniformly goldish with no stripes, so A.frankii?