The one specimen is from the pine forests on the Cordillera Volcánica. At the present time this species is known from scattered localities in west-central Veracruz, Oaxaca, Michoacán, and as Crotalus intermedius omiltemanus in Central Guerrero. Apparently it is restricted to montane environments.
Crotalus molossus nigrescens Gloyd
Crotalus molossus nigrescens Gloyd, Occ. Pap. Mus. Zool. Univ. Michigan, 325:2, January 28, 1936.—Four miles west of La Colorada, Zacatecas, México.
Carapan; Los Conejos; Pátzcuaro; Tacícuaro (5).
In Michoacán this species has been found in pine forests between 1550 and 2300 meters in the Cordillera Volcánica. I expected to find it in the Sierra de Coalcomán, but inquiries among the natives living in the pine forests of that mountain range revealed that the people there have no knowledge of a large species of rattlesnake.
Crotalus polystictus (Cope)
Caudisonia polysticta Cope, Proc. Acad. Nat. Sci. Philadelphia, 17:191, December 26, 1865.—Tableland of México. Type locality restricted to Tupátaro, Guanajuata, México, by Smith and Taylor (1950a:330).
Crotalus polystictus Cope, in Yarrow, Wheeler's Rept. Geog. Geol. Expl. Surv. W. 100th. Mer., vol. 5, p. 533, 1875.
Tacícuaro (4); Tupátaro (2).
Formerly this species was abundant in the marshes around Lago de Chapala. The draining of these marshes probably resulted in reducing the numbers of these rattlesnakes. The species is known only from the Mexican Plateau at elevations of 1450 to 2400 meters.