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BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32
variable with respect to the white component of the
dorsum, this variation was coded as an unordered
multistate character. The Gambelia condition often
consists of broad, white or cream-colored, offsetting
transverse bars with large, brown dorsal spots and
is coded as state 0; the C. reticulatus and C. antiquus
condition of a white reticulum, some or all of which
enclose black pigmentation, is coded as state 1; the
pattern composed of numerous small white spots
(present in C. bicinctores, C. collaris, C. dickersonae,
C. grismeri, and C. nebrius) is coded as state 2; the
C. vestigittm condition of white, transverse dorsal
bands on a background of white spots and dashes
is coded as state 3, and the C. insularis condition
of wavy, white dorsal dashes is coded as state 4.
This character was left unpolarized.
Sesual Dichrornatism (Character 69; Fig. 3 1 B,
C).-Sexual dichromatism is widespread within the
Iguania (Cooper and Greenberg, 1992) and, thus, it
is not surprising that most crotaphytids also display
strong sexual dichromatism. However, Gambelia
and Crotaphytus reticulatus generally lack sexual di-
chromatism in their permanent dorsal patterns (al-
though G. silus and C. reticulatus do have male
breeding coloration). There is obvious sexual di-
chromatism in the gular pattern and femoral pore
coloration and a small amount of sexual variation
in the collar of C. reticulatus. However, the re-
maining species of Crotaphytus have much more
obvious sexual dichromatism throughout the year,
with males differing from females in most aspects
of dorsal coloration (e.g., much more vibrant blue,
green, and/or yellow dorsal coloration in C. collaris),
as well as in the gular pattern. Although sexualdi-
chromatism is present in many iguanian taxa, data
could not be obtained for many of the more obscure
and poorly known species. Therefore, this character
was left unpolarized.
Paired Melanic Keels on Scales of Ventral Caudal
Extremity (Character 70). -All Crotaphytus species
except C. reticulatus (50 specimens examined) and
C. insularis (23 specimens examined) are charac-
terized by the presence, in at least some individuals,
of darkly pigmented obtuse keels on the scales of
the ventral surface of the tail tip (noted as present
in C. nebrius and some C. collaris by Axtell and
Montanucci, 1977). These take the appearance of
paired dark spots that may extend along the ventral
surface of the tail over the distal 2-30 mm. This
feature is fixed in some species, polymorphic in oth-
ers, and the percentage of individuals with the pig-
mented keels may vary extensively between popu-
lations of the same species.
Crotaphyt~ts collaris is polymorphic with respect
to this character and there is much geographic variation
in the percentage of individuals with the paired
pigmented scales. Individuals from regions of Mexico
generally referred to the subspecies C. c. firsclcs
and C. c. baileyi usually possess this character (2 1
of 33 specimens examined). It is less often present
(six of 23) in specimens from midwestern and southern
United States (generally referred to the subspecies
C. c. collaris). It was absent in all specimens of
C. collaris examined from Arizona, eastern Utah,
and western Colorado (generally referred to the subspecies
C. c. baileyi and C. c. auriceps, n = 38).
Although the percentage of individuals with pigmented
keels varies regionally, the observed frequency
for C. collaris (29 of 94) was employed in
the phylogenetic analysis.
In Crotaphytus nebrius, this characteristic appears
to be nearly fixed. The pigmented scales were observed
in 48 of 49 specimens examined. The only
specimen that lacked the scales (KU 12 1460) was
from the Tucson Mountains, an isolated range inhabited
by what may be a distinct species. Unfortunately,
this is one ofonly two preserved specimens
available from the Tucson Mountains (the other
specimen, SDSNH 15208, had pigmented scales).
The pigmented scales are much darker, and thus
more obvious, in C. nebriics than in C. collaris.
Crotaphytw bicinctores is another species in which
this characteristic is polymorphic. It was present in
37 of 79 specimens examined. However, the percentage
of individuals with the pigmented scales
varied considerably between populations. Specimens
from southern populations (Palo Verde
Mountains, California; Chocolate Mountains, California;
Kofa Mountains, Arizona; Sentinel, Arizona)
have the scales in high frequency (26 of 32),
while specimens from more northern populations
(Idaho; Inyo County, California; Washington County,
Utah) usually lack them (present in three of 30
specimens examined).
The pigmented scales appear to be fixed in Crotaphytus
dickersonae (present in 44 of 44 specimens
examined), C. grismeri (present in ten of ten specimens
examined), C. vestigium (present in 43 of 43
specimens examined), and in C. antiquus (present
in 17 of 17 specimens examined). The presence of
paired melanic keels on the distal caudal extremity
is considered to be the derived state as they appear
to be unique to Crotaphytus.
Black Oral Mucosa (Character 7 I).-In all crotaphytids
except Crotaphyttcs bicinctores, C. gristneri,
C. insularis, and C. ~~estigium, black pigments