Although Michoacán has not previously been included in the range of this lizard, it was first collected in the state by Gadow in 1908 (BMNH 1914.1.28.69 from Araparicuaro). The description of S. heterolepis given by Smith (1939:197) can be supplemented by data on the 23 specimens now in the collections of the Museum of Zoology at the University of Michigan. All have two canthals; there are 55 to 71 (63.6) scales in the middorsal row; 1 to 3 rows middorsally are somewhat enlarged and bordered on either side by a row of larger scales bearing high keels. There are 14 to 20 (16.2) femoral pores. Eight adult males have snout-vent lengths from 49 to 61 (58.0) mm. and tail lengths from 57 to 74 (66.0) mm.; four adult females have snout-vent lengths from 52 to 57 (55.2) mm. and tail lengths from 60 to 66 (63.5) mm. The smallest of eight juveniles has a snout-vent length of 28 mm. and a tail length of 32 mm. The dorsum in adults is pale grayish brown; there are three irregular chevron-shaped dark marks and a triangular dark brown mark above the insertion of the hind limbs; on the tail are dark brown rings. There are scattered faint blue flecks on the flanks and narrow transverse dark lines on the lower limbs. Males have pale bluish green belly patches and an orange-salmon-colored throat; the belly in females is pale orange-tan. The juveniles have a more contrasting color pattern; the dark chevrons on the dorsum are bordered posteriorly by pale gray.
In Michoacán this species has been obtained in pine and pine-fir forests from 1800 to 2700 meters. On Cerro Barolosa and at Dos Aguas, both in the Sierra de Coalcomán, the lizards were found beneath the bark of dead, standing pines. In the Sierra de Coalcomán Sceloporus heterolepis seems to fill the niche of the small arboreal Sceloporus in the coniferous forest in southwestern México, a position held by S. grammicus microlepidotus in the Cordillera Volcánica; the latter species does not occur in the Sierra de Coalcomán. Five specimens of Sceloporus heterolepis are known from the Cordillera Volcánica, whereas 603 of S. grammicus microlepidotus have been collected there. The ecological relationships that exist between the two species in the Cordillera Volcánica are not known.
Insofar as is known, Sceloporus heterolepis reaches the southern limits of its range in the Sierra de Coalcomán and in the western part of the Cordillera Volcánica. Other records for the species are from the Sierra Madre Occidental in Jalisco. Langebartel (1959) described Sceloporus shannonorum from the mountains near the Durango-Sinaloa border; the single specimen of S. shannonorum differs significantly from S. heterolepis only in having fewer dorsal scales (48). The acquisition of additional material, especially from Nayarit and northern Jalisco, probably will provide a basis for showing that these two populations are conspecific.
Sceloporus horridus oligoporus Cope
Sceloporus oligoporus Cope, Proc. Acad. Nat. Sci. Philadelphia, 16:177, September 30, 1864.—Colima, Colima, México.
Sceloporus horridus oligoporus, Taylor, Univ. Kansas Sci. Bull., 24:520, February 16, 1938.
Aguililla; Apatzingán (50); Arteaga (2); Capirio (2); Cascada Tzararacua; Charapendo (4); Coahuayana (3); Coalcomán (32); 19 km. S of Corralito; 27 km. E of Dos Aguas; El Sabino (55); El Ticuiz; Huetamo (2); Jazmin; Jungapeo (2); La Orilla (2); La Placita; Limoncito (3); Playa Azul (5); Tzitzio (8); Uruapan (4); Volcán Jorullo (2); Ziracuaretiro; Zirimícuaro (13).
All of the specimens from Michoacán seem to be typical S. horridus oligoporus; none has more than six femoral pores.
Characteristically this species is found in open arid scrub forest; it reaches its greatest abundance in rocky areas in which there are scattered leguminous trees and bushes. It has been found in these low trees and bushes almost as frequently as it has been found on the ground; none has been seen in large trees or far above the ground. Altitudinally, this species ranges from sea level to about 1600 meters.
Sceloporus melanorhinus calligaster Smith