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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 color-
ation, 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 en-
larged middorsal series may be present. Nasals sep-
arated by six to nine internasals. Frontonasals oc-
casionally enlarged. Canthals four; posterior one or
two wider than high; six to ten scales separate can-
thals 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) de-
velop 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 ven-
tral surface of the body and limbs, sometimes in-
cluding the gular region as well (Montanucci, 1965).
Occasionally, individuals may develop this color-
ation only laterally (Montanucci, 1970). Gravid col-
oration 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 occa-
sionally 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-