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102 BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32
Il1usrrations.-Black-and-white photographs of
adult lizards were provided in Banta and Tanner
( 1968) and Montanucci (1 978).
Taxonotnic Remarks.-Gambelia copei and G.
wislizenii are easily distinguished on the basis of
their coloration (see diagnosis above). However,
geographic variation in the dorsal coloration of
Gambelia wislizenii is extensive and this alone is
not particularly compelling evidence for the recog-
nition of copei as a distinct species. The primary
motivation for this taxonomic rearrangement is the
occurrence of both forms in syntopy along a narrow
zone within Paseo de San Matias in northeastern
Baja California. Within Paseo de San Matias, in-
dividuals that are easily identified to species occur
together in the same microhabitat over a zone of
1.6 km without showing any obvious evidence of
intergradation. Aside from this narrow contact zone,
the distributions of G. copei and G. tvislizenii are
widely separated.
Paseo de San Matias is a low elevation dispersal
corridor that connects the lower Colorado Desert
with the coastal region of northwestern Baja Cali-
fornia. Several desert species extend their ranges
westward toward the Pacific coast by way of this
corridor and some coastal species nearly reach the
desert by extending eastward (Welsh and Bury,
1984). It may appear as though G. copei and G.
tvislizenii are geographic variants and that the pat-
tern change is the result of in situ selection where
the habitat changes from extremely xeric creosote
desert to more mesic mountainous terrain. How-
ever, typical G. copei occur in the lower Colorado
Desert region in the vicinity of Bahia de San Luis
Gonzaga, documenting that the distinctive color
pattern of G. copei is not another G. rvislizenii pat-
tern type that appears only in mesic habitats. Gam-
belia copei in the Bahia de San Luis Gonzaga region
are approached by G. wislizenii in the vicinity of
Puertocitos, where they are separated by a trans-
verse volcanic field that is 31.5 road km in width.
This lava field extends from the peninsular ranges
to the edge of the Gulf of California and appears to
be a dispersal bamer for Gantbelia. Because the
color pattern differences noted above are main-
tained in these populations, which occur in essen-
tially identical habitats that are separated only by
the lava field, the notion that the G. copei and G.
wislizenii color pattern differences are the result of
in situ selection is unlikely. Nevertheless, because
this taxonomic decision is based only on differences
in coloration that are relatively subtle, on a single
osteological character that differs in frequency (the
presence of a well-developed tubercle on the an-
terolateral margin of the postorbital was present in
all G. copei examined [n = 81, whereas in G. wisli-
zenii, the tubercle usually is absent [present in four
of 49 specimens]), and on presumed reproductive
isolation in this region, the recognition of G. copei
as a full species is considered tentative. Electropho-
retic analyses of the Paseo de San Matias popula-
tions are planned in order to determine if fixed al-
lelic differences can be detected that are consistent
with the dorsal color pattern data.
Montanucci (1978) considered the populations of
Gantbelia on Isla Tiburon and coastal Sonora be-
tween Puerto Libertad and Bahia Kino to be
con(sub)speci fic with copei. Although there are no-
table similarities between certain individuals from
the coastal Sonoran region and those from Baja Cal-
ifornia (particularly in CAS 17050 from the south-
eastern end of Isla Tiburon), they differ in that the
Sonoran lizards have spots that continue onto the
dorsal surface of the head, whereas G. copei nearly
always lack this spotting. While some individuals
from coastal Sonora clearly resemble those of Baja
California, the majority examined here were char-
acteristic of those of the remaining portions of So-
nora.
Gantbelia coronat Norell
Gantbelia corona Norell, 1989:ll; fig. 10. Type locality: LACM
locality 7058, Vallecito Badlands, Anza-Borrego Desert State
Park (holotype: LACM 42880).
Er)~mology.-From the Latin corona, a crown, in reference to
the distinctive characteristics of the frontal and irontoparietal
suture.
Diagnosis. - Gambelia coronat is distinguished
from other Gambelia by the presence of the fron-
toparietal suture anterior to the posterior extent of
the orbits. It is further distinguished from Gambelia
copei and G. tvislizenii by the presence of a trans-
versely concave frontal bone.
Distribution. -Known only from the type locality.
Rentarks. -Gambelia coronat is an extinct spe-
cies known only from a fossilized skull and man-
dibles. Black-and-white photographs of dorsal and
lateral views of the skull were provided by Norell
(1 989).
Gambelia silus Stejneger
Croraphytus silus Stejneger, 1890: 105. Typ locality: "Fresno,
Cal." (holotype: USNM 1 1790A).
Cruraphytus ~vislizenii-Cope, 1 900:255.