Originally described from Grutas de Zapaluta in Chiapas, Mexico by Mullinex (1975). Now suggested to range from Oaxaca to Central Guatemala (See. Ballestros, 2010). Not mentioned by Viquez & Armas (2006)
From Mullinex 1975 (page.14-15): "Medium sized species (length of holotype 20 mm.); color in alcohol pale brown. Resembles P. macrops, P. leptus and P. emaciatus in the following ways: Bd-I longer than Bd-III (fig. 12e); difference in length between first and second ventral spines of pedipalp femur considerably less than difference in length between second and third spines, so that these first three spines do not appear to diminish evenly in length (fig. 12c); dorso-inner lateral surface of proximal end of pedipalp tarsus with a small inconspicuous spine (fig. 12g); pedipalp tarsus and post-tarsus not fused; i.e. these two areas are separated by a suture (fig. 12g). Can be distinguished from P.leptus and P. emaciatus in the following ways: P. williamsi with Bd-III longer than spine IX on dorsal surface of tibia (fig. 12b, e); inner lateral surface of pedipalp basitarsus smooth with only a few marginal coarse granules (fig. 12e). Paraphrynus leptus and P. emaciatus with Bd-III shorter than spine IX on dorsal surface of tibia (figs. 15b, e, 17b, e), and with inner lateral surface of pedipalp basitarsus appearing rougher because of numerous fine and coarse granules (figs.15e , 17e)."