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1996 McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 103 Gatttbelia wislizenii silus-Smith, 1946: 164; pl. 3 1. Croraphytrc~ (Gatnbelia) wislizeni silus-Weiner and Smith, 1965: 187. Ganibelia silus-Montanucci, Axtell, and Dessauer, 1975:339. Gambelia silo-Jennings. 1987: 1 I. Etymology. -From the Latin siltcs. snub-nosed. in reference to the blunt snout of this species. Diagnosis. - Gambelia silus is diagnosed from G. coronat by the presence of a frontoparietal suture that is posterior to the posterior border of the orbits. It is diagnosed from G. \vislizenii and G. copei by the presence of territoriality, male breeding coloration, vertebrae with notched zygosphcnes and zyg- antra, sexual dimorphism wherein males are larger than females, and in its truncated snout. Variation (n = 15).-Rostra1 approximately four times wider than high, usually rectangular in shape. Rostra1 bordered by six to eight postrostrals. Re- maining snout scales irregularly arranged, an enlarged middorsal series may be present. Nasals separated by six to nine internasals. Frontonasals occasionally enlarged. Canthals four; posterior one or two wider than high; six to ten scales separate canthals of left and right sides. Supraorbital semicircles absent, although slightly enlarged scales correspond- ing to the supraorbital series occasionally evident. Supraoculars small, flat or convex, smooth, becom- ing progressively larger medially such that medial scales are two to four times larger than lateral ones. Circumorbitals absent. Superciliaries eight to 13, extremely elongate medial scale present. Palpebrals ovoid, slightly convex, may be interspersed with numerous interstitial granules. Preoculars, subocu- Ian, and postoculars form an arc of five to eight rectangular scales, second, third, or founh scale elongate. Supralabials 13 to 16, usually slightly lon- ger than high except anteriormost scale, which is square. Lorilabials in one to four rows, ovoid to rectangular, juxtaposed, separating supralabials from suboculars and nasals. Aperture of external auditory meatus rectangular or ovoid, often constricted at or above the midpoint, approximately three to four times higher than wide, with small, strongly convex, somewhat conical auricular scales lining anterior margin. Mental pentagonal, one to 1.5 times wider than high, bordered laterally by anterior infralabials and posteriorly by a pair of enlarged postmentals. Postmentals separated from infralabials by subla- bials on at least one side. Chinshields weakly dif- ferentiated or undifferentiated. Infralabials 12 to 16, square or wider than high, inferior border convex. Gulars convex and beadlike; each scale separated from adjacent scales by numerous asymmetrically arranged interstitial granules. Dorsal scales in approximately 156 to 182 rows midway between forelimb and hindlimb insertions. Tail long, cylindrical in both sexes and all age groups. Paired, median row of subcaudals not larger than adjacent subcaudals and lateral caudals. Enlarged postanal scales present in males. Deep postfemoral dermal mite pocket present at hindlimb insertion. Femoral pores 1 5 to 20, femoral pores do not extend beyond angle of knee, separated medially by 17 to 25 granular scales. Subdigital la- mellae on founh toe 16 to 20. Coloration in Life. -The dorsal base color ranges from pale tan, light or dark gray, or brown and the ventrum is white or yellowish. The dorsum is marked with seven to ten broad, pale transverse bars that may or may not be offsetting. Dark spots are often present between the pale crossbars and generally extend onto the temporal region of the head. The crossbars occasionally may be fragmented into light spots and a vertebral stripe may be present (Mon- tanucci, 1965). Spots and crossbars similar to those of the back are generally present on the limbs and tail, although the crossbars may be absent from the forelimbs. The tail becomes banded distally as de- scribed in the generic account. The posterior of the thigh and the underside of the tail in juveniles is suffused with yellow pigments. Males in certain parts of the range (particularly the foothills surrounding the San Joaquin valley) develop a breeding color composed of either a bright rusty red suffusion of the abdomen and the ventral and dorsal surfaces of the hindlimbs and tail or a bright salmon color that extends over the entire ventral surface of the body and limbs, sometimes including the gular region as well (Montanucci, 1965). Occasionally, individuals may develop this coloration only laterally (Montanucci, 1970). Gravid coloration in this species is similar to that of G. copei and G. wislizenii in that the orange or red pigments are deposited on the lateral surfaces of the head and flanks, on the under surface of the tail, and occasionally on the thighs. However, this pattern differs from that of G. copei and G. wislizenii in that the pigments are generally deposited in a single row along each flank, rather than in two rows (Montan- ucci, 1970). The dorsal pattern of Garnbelia silus was de- scribed more fully in Van Denburgh (1922), Smith (1946), and Montanucci (1965, 1970). Size. -This species exhibits strong sexual dimor-
BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32 phism with males reaching larger adult size (maximum observed SVL = 120 mm) than females (maximum observed SVL = 11 1 mm; Tollestrup, 1979, 1982). Distribution (Fig. 5 1). - Gatnbelia silus is restricted to the San Joaquin valley of California and its surrounding foothills. They range between "the old town of Carnegie in Corral Hollow," San Joaquin County, in the north to the Cuyama Valley and base of the Tehachapi <strong>Mountain</strong>s in the south. The species apparently does not contact G. trlislizenii presently, although Montanucci (1 970) identified an isolated population of putative hybrid origin between the two species in the Cuyama River drainage system southwest of the southern end of the San Joaquin valley. Although G. siltrs and G. tvislizenii are isolated from one another, Gatnbelia tvislizenii approaches G. sifus in the Cuyama valley drainage where G. bvislizenii occurs above 1100 m and G. silus occurs below 790 m (Montanucci, 1970). Fossil Record.-No fossil specimens have been referred to this species, although Bratts~rom (1953) considered measurements of two maxillae taken from McKittrick, Kern County, California, a locality within the current distributional confines of Gatnbelia silus, to conform more closely to extant G. tvislizenii than to G. silus. However, examination of his figures renders this observation suspect as neither fossil has a complete nasal process. On distributionalgrounds, it would appear more likely that these specimens represent G. silus. Because the material has not been reexamined here, the reference to G. tvislizenii is considered questionable. Natural History. -Montanucci (1 965, 1967, 1970) and Tollestrup (1 979, 1982, 1983) studied the ecology of Gatnbelia silus and all of the comments provided here are taken from these references unless otherwise noted. According to Montanucci (1965), the species inhabits sparsely vegetated plains, alkali flats, low foothills, canyon floors, large washes, and arroyos. They prefer open habitat and are absent or rare in areas with dense vegetation or tall grass. As is the case with G. tvislizenii, the species appears to be most common in areas with abundant rodent burrows. Common vegetational associates include grasses (Stipa), saltbush (Atriplex), and iodinebush (Allenrofia occidentalis). In contrast with Gatnbelia ir)islizenii (and presumably G. copei), G. silus is highly territorial and males from many, but not all, populations develop rusty red coloration during the breeding season (Montanucci, 1 965; Tollestrup, 1 979, 1 982). The activity season commences in late March or early April and extends through late September, although some juveniles may remain active into October given fa- vorable weather conditions (Montanucci, 1965; Tollestrup, 1979). The mating season occurs primarily in late April and May, although Germano and Williams (1 992) observed gravid females as late as midJuly, and young hatch in late July or early August (Montanucci, 1965; Tollestrup, 1979, 1983). Clutch size is smaller than that of G. tvislizenii, with a range of two to six and a mean of 2.90 (Tollestrup, 1979, 1982) to 3.30 (Montanucci, 1970). Germano and Williams (1992) documented that as many as four clutches may be deposited per reproductive season. Ganibelia silus shares a number of behavioral similarities with G. copei and G. ivislizenii. All three are often observed basking on small roadside rocks and the berms along the edges of graded din roads. "Freeze" behavior (Montanucci, 1965), wherein threatened individuals run to the base of a nearby bush, flatten themselves to the ground, and remain motionless (presumably as a means of avoiding de- tection) is also a shared behavior. Montanucci (1 965) indicated that Gambelia silus feeds primarily upon locusts (Onhoptera), cicadas (Homoptera), and small lizards, including Uta stansburiana, Phrynosorna coronaturn, Cnernidoph- orus tigris, and Sceloporus magister. Germano and Williams (1994) observed that G. silus eat young conspecifics, as well. Tollestrup (1 979) found no ev- idence of lizard predation at her southern San Joa- quin valley study sites and noted the following ar- thropod prey items: orthopterans, coleopterans, hy- menopterans, dipterans, homopterans, lepidopter- ans, and spiders. Regional or seasonal variation may explain the discrepancies in food preferences found in these studies. Montanucci (1965) noted predation on Gambelia silus by several avian species including Loggerhead Shrikes (Lanius ludoviciantcs), American Kestrels (Falco sparverius), Burrowing Owls (Athene cuni- cularia), and Greater Roadrunners (Geococcyx cal- fornianus). Prarie Falcons (Falco tnexicanus) are also known to capture this species (Germano and Caner, 1995). Montanucci (1 965) also observed predation by the coachwhip snake (Masticophisfla- ge/lttttn) and the gopher snake (Pituophis melano- leuctrs). Other potential predators include the spot- ted skunk (Spilogaleputorius) and the ground squir- rel (Spertnophilus beecheyi), both of which con- sumed G. silus when captured together in barrel traps, as well as the coyote (Canis latrans), badger (Taxidea taxtcs), glossy snake (Arizona elegans), long-
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