Global Range: (20,000-200,000 square km (about 8000-80,000 square miles)) Range includes the Rio Grande watershed of Texas and northeastern Mexico from Brownsville northward to Brewster County, Texas (Bailey et al. 2005), and the Pecos River drainage of northwestern Texas (Culberson, Reeves, and Loving counties) and southeastern New Mexico, north to Brantley Reservoir (Ernst 1990, Degenhardt et al. 1996). Occurrences in Mexico are known from Coahuila, central Nuevo Leon, and northeastern Tamaulipas (Ernst 1990). In August 2007, Farr photographed individuals 0.5-4 km south of the river near Ciudad Miguel Alemán, Mexico, across from Roma, Texas (Bailey et al. 2008). Elevational range extends from sea level to around 1,100 meters (900-1,100 meters in New Mexico) (Degenhardt and Christiansen 1990, Degenhardt et al. 1996).
A 1998 record also exists for Menard County, Texas, about 170 km northeast of the nearest previously documented locality (Franklin and Reams 2001). This was an adult male found on the shoulder of a road, so additional study is needed to determine whether this record represents an established population or a translocated individual.
A specimen from "Blue Springs" in Eddy County, New Mexico, probably came from the Black River, a tributary of the Pecos River (Legler 1958).
Bailey et al. (2008) found P. gorzugi at low density and with a significant hiatus in the middle reaches of the Pecos River from the New Mexico border southward to the confluence with Independence Creek in Terrell County. Bailey et al. (2008) and W. Farr (Houston Zoo) were unable to locate individuals in the main channel of the Rio Grande south of Roma, Texas.
A sketchy record from the Bitter Lakes National Wildlife Refuge, Chaves County, New Mexico (Bundy 1951), may be erroneous; Degenhardt et al. (1996) questioned the identification (no specimen is known to exist), and recent searches for the species there have been unsuccessful.
See Ernst and Lovich (2009) for a recent map of the known distribution.