William Edward Duellman

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The systematic status of the populations of lizards assignable to Cnemidophorus sacki in western MÉxico (Sonora southward to Jalisco) has been reviewed in detail by Zweifel (1959, Bull. Amer. Mus. Nat. Hist, 117 (2):57-116), who stated that the use of the specific name sacki for the western populations rests upon a reasonable, but as yet unproved, assumption that intergradation occurs. Although Zweifel examined specimens of the nominal subspecies from the upper Balsas Basin, he did not study specimens from the intervening area—the Tepalcatepec Valley in MichoacÁn.

Field studies and the examination of large series of preserved specimens of Cnemidophorus from the Tepalcatepec Valley show the presence of Cnemidophorus sacki in the region between the ranges of C. sacki sacki in the upper Balsas Basin and C. sacki occidentalis in Jalisco and southern Nayarit. Furthermore, the populations of sacki inhabiting the Tepalcatepec Valley have characters of scutellation and coloration that distinguish them from other described subspecies of sacki. In recognition of the important contributions to the systematics of the genus Cnemidophorus made by Dr. Richard G. Zweifel, I propose that the subspecies of Cnemidophorus sacki in the Tepalcatepec Valley be named as follows:

Ontogenetic Change in Color Pattern.—The metamorphosis of color pattern in Cnemidophorus sacki zweifeli results in the dorsal ground-color becoming paler with age, the replacement of the stripes by spots, and finally in large males the suffusion of these spots.

A single hatchling (UMMZ 114732) is available; this specimen has a prominent umbilical scar and a snout-vent length of 34 mm. The top of the head is olive brown; the dorsal surfaces of the limbs are dark brown with cream mottling; the dorsal ground-color is brownish black; this is paler on the lower flanks. The lateral and dorsolateral stripes are cream-colored; the paravertebral stripes are white. There is a faint, diffuse vertebral stripe anteriorly (Fig. 2 A). The throat and undersides of the limbs and tail are cream-colored; the belly is bluish white. In life the stripes were pale yellowish green, and the tip of the tail was pink.

In larger individuals the dorsal ground-color is dark brown; the lower flanks are grayish tan. Light brown diffuse spots are present in the lateral and dorsolateral dark fields. The tan vertebral stripe is diffuse and nearly fills the paravertebral dark fields; the paravertebral stripes are faint posteriorly; throughout their length they are scalloped—the beginning of their fragmentation into spots (Fig. 2 B).

In subadults (± 80 mm. snout-vent length) the paravertebral stripes are fragmented into spots posteriorly. Also, the dorsolateral stripes in some individuals are fragmented posteriorly. The dorsolateral dark fields are somewhat paler than the lateral dark fields. Cream-colored spots are present on the flanks. The mottling on the thighs tends towards the formation of light spots (Fig. 2 C).

In small adults (± 100 mm. snout-vent length) the paravertebral stripes are entirely fragmented into spots. The lateral and dorsolateral stripes are broken into spots posteriorly. The middorsal pale area (formed by the suffusion of the vertebral stripe) and paravertebral and dorsolateral rows of spots are pale green. The cream-colored spots on the flanks are expanded to form vertical bars (Fig. 2 D).

Large adult males (± 120 mm. snout-vent length) have all of the stripes fragmented into spots. The diffuse middorsal area is expanded and encloses the paravertebral rows of spots. The pale spots present in the dark fields in smaller individuals are either absent or fused with spots resulting from the fragmentation of the stripes (Fig. 2 E).

Sexual dimorphism.—Males attain a larger size (known maximum snout-vent length of 132 mm., as compared with 114 mm. in females). Males have larger but not more numerous, femoral pores, blue bellies, and pink and blue throats, whereas females are unicolor creamy white ventrally. The more nearly complete metamorphosis of color pattern exhibited by adult males probably is correlated with their large adult size. Large females retain complete lateral and dorsolateral stripes. The jowls of breeding males are swollen.

Geographic variation.—No noticeable geographic variation in this subspecies is evident in the series from the Tepalcatepec Valley. However, lizards from eastern MichoacÁn (Chinapa, 6 km. N of Tafetan, 6 km. S of Tzitzio, and 19 km. S of Tzitzio) differ slightly from those from the Tepalcatepec Valley; the eastern specimens have fewer dorsal granules and femoral pores, and a higher ratio of dorsal granules between the paravertebral stripes to the number of granules around the body (see Tables 1-3). No large adult males are present in the eastern series; the subadults and small adult males have color patterns like lizards of similar size from the Tepalcatepec Valley. The largest male from the east has a snout-vent length of 110 mm., rows of pale spots, and no trace of brown and tan cross-bars. Specimens of Cnemidophorus sacki sacki of equal size from Guerrero, Morelos, and Puebla in the upper Balsas Basin have a tan dorsum with dark brown cross-bars. The localities in eastern MichoacÁn are intermediate geographically between the Tepalcatepec Valley and the known range of the nominal subspecies in the upper Balsas Basin. In characters of scutellation specimens from the east are intermediate between C. sacki sacki and C. sacki zweifeli in the Tepalcatepec Valley. However, in coloration the lizards from the east are like those from the Tepalcatepec Valley, but differ distinctly from the nominal subspecies. Therefore, the eastern series is referred to the subspecies C. sacki zweifeli.

Comparisons.—Four other species of Cnemidophorus occur in the Tepalcatepec Valley with Cnemidophorus sacki zweifeli. Of these, C. calidipes has a maximum snout-vent length of 79 mm., 66 to 86 dorsal granules, and a light brown dorsum with pale blue spots and vertical bars; C. communis communis has a maximum snout-vent length of 135 mm., 105 to 144 dorsal granules, and a greenish tan dorsum with yellow spots; C. deppei infernalis has a maximum snout-vent length of 84 mm., 91 to 120 dorsal granules, and a striped pattern throughout life; and C. lineatissimus exoristus has a maximum snout-vent length of 98 mm., 108 to 135 dorsal granules, and a middorsal yellow stripe and vertical bars on the flanks. Both calidipes and communis are like sacki in possessing four enlarged supraoculars and enlarged postantebrachials, whereas deppei and lineatissimus have three enlarged supraoculars and granular postantebrachials. Juveniles of calidipes and sacki are alike in coloration but different in the extent of the supraorbital semicircle-series. In calidipes the supraorbital semicircle-series usually are complete, whereas in sacki the series never extended anterior to the posterior edge of the frontal.

From the geographically adjacent populations of sacki (sacki and occidentalis), zweifeli differs in coloration and scutellation (see Tables I-III). Cnemidophorus sacki sacki has a dorsal pattern in adult males of dark brown cross-bars on a tan ground-color. Both occidentalis and zweifeli have variable, diffuse color patterns in large adults, but zweifeli differs from occidentalis in having a blue spot on the pink throat.

Ecology.—In the arid Tepalcatepec Valley Cnemidophorus sacki zweifeli lives at elevations of 160 to 1300 meters. In the lower parts of the valley the lizards live primarily in open scrub forests, characterized by deciduous trees offering only partial shade from the sun, especially during the prolonged dry season. Common trees in this scrub forest are Acacia cymbispina, Cercidium plurifoliolatum, Mimosa distachya, and Prosopis juliflora.

During the dry season (November through May) adult males apparently aestivate; several large series collected in the winter include only subadults and females. This absence of males is corroborated by personal observations in the Tepalcatepec Valley in April and May. In the summer rainy season the lizards are active in the morning and again in the late afternoon; only Cnemidophorus calidipes is active during the heat of the midday. In some areas of the scrub forest Cnemidophorus sacki zweifeli is found in association with Cnemidophorus communis communis. Throughout the scrub forest C. sacki zweifeli occurs with C. deppei infernalis. In some of the more dense scrub forest, where C. sacki zweifeli is not so abundant as in the more open forest, it has been taken with C. lineatissimus exoristus. In the open Acacia-Cercidium associations on the valley floor C. sacki zweifeli occurs with C. calidipes.

This subspecies is not restricted to the scrub forest. On the lower slopes of the Cordillera Volcanica in MichoacÁn C. sacki zweifeli has been collected in open pine-oak forest near Zirimicuaro and Ziracuaretiro.

Distribution.—Cnemidophorus sacki zweifeli inhabits the valley of the RÍo Tepalcatepec in MichoacÁn and probably extreme southwestern Jalisco, and the western part of the Balsas Basin in MichoacÁn. No specimens have been seen from extreme western Guerrero, but C. s. zweifeli may occur there.

Transmitted February 2, 1960.