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1996 McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 79
the natural history of this species than any other
Crotaphytus, with the major ecological study being
Fitch (1956). Numerous unpublished master's the-
ses and Ph.D. dissertations have dealt with ecology
of C. collaris including (but not necessarily limited
to) Mosley (1 963), Trauth (1974), Hipp (1 977). Bon-
trager (1980), McAllister (1980), Rostker (1983),
Malaret (1 985), Rand ( 1986), and Uzee (1 990). More
specific published works have dealt with feeding
(Burt, 1928a; Blair and Blair, 194 1 ; McAllister and
Trauth, 1982), growth (Sexton et al., 1992), endo-
parasites (McAllister, 1985), reproduction (Green-
berg, 1945; Clark, 1946; Robison and Tanner, 1962;
Cooper and Ferguson, 1972, 1973; Parker, 1973;
Ferguson, 1976; Trauth, 1978, 1979; Montanucci,
1983; Ballinger and Hipp, 1985), territoriality and
aggression (Greenberg, 1945; Yedlin and Ferguson.
1973; Fox and Baird, 1992), hibernation (Legler and
Fitch, 1957), aquatic behavior (McAllister, 1983),
and thermoregulatory behavior (Dawson and Tem-
pleton, 1963; Cothran and Hutchison, 1979) to
highlight just a small sample of the vast amount of
literature pertaining to this species.
Illustrations. -Numerous illustrations and pho-
tographs have appeared in publications and this list,
by necessity, is not intended to be complete. Pub-
lished figures include black-and-white illustrations
of the entire animal (Harlan, 1835; Holbrook, 1842;
Baird, 1859). head squamation (Baird, 1859; Stejne-
ger, 1890; Cope, 1900; Bun, 19286; Stebbins, 1954,
Ingram and Tanner, 197 l), dorsal pattern (Ingram
and Tanner, 197 1; Smith and Tanner, 1974), limb
and preanal squamation (Cope. 1900). and skull,
pectoral girdle, and pelvic girdle (Weiner and Smith,
1965). Black-and-white photographs are found in
Ditmars (1 920) and Van Denburgh (1 922); color
plates in Ditmars (1920), Webb (1970), Stebbins
(1 985), Dundee and Rossman (1 989), and Conant
and Collins (1 991); color photographs in Cochran
and Goin (1970), Leviton (197 I), Behler and King
(1 979), Collins (1 982), Hammerson (1 986), Garrett
and Barker (1 987), Johnson (1 987), and Sprackland
(1990, 1993). Color photos showing greater road-
runners (Geococcyx californianus) capturing and
consuming C. collaris were presented by Meinzer
(1 993).
Taxonomic Remarks. -As discussed in the Ma-
terials and Methods section, all of the subspecies of
C. collaris except C. nebrius (C. c. auriceps, C. c.
baileyi, C. c. jiuscus, and C. c. melanomaculatus) are
here synonymized with C. collaris because no evi-
dence has ever been presented, nor has any been
discovered here, that these taxa represent indepen-
dent lineages. For example, Ingram and Tanner
(1971) showed the intergrade zone between C. c.
auriceps and C. c. baileyi to be larger than the range
of C. c. attriceps itself. The only characters that have
been presented that are thought to separate C. c.
baileyi from C. c. collaris are the following C. c.
collaris features: supraorbital semicircles fused medially
to form one or more azygous frontal scales,
gular pouch yellow-orange, a shorter broader head,
and larger supraocular scales. Of these, the first two
are usually considered to be the principle diagnostic
features (Brown, 1903; Meek, 1905; Ruthven, 1907;
Strecker, 1909; Burt, 19286; plus numerous other
references) and both intergrade extensively. The
condition of the supraorbital semicircles varies considerably
in Colorado, New Mexico, and Texas populations
(Burt, 1928b; personal observation), which
prompted Burt (19286) to synonymize C. c. baileyi
with C. c. collaris. The yellow-orange gular pattern
of C. c. collaris occurs at least as far south as Fredericksburg,
Gillespie County, in southern Texas. Individuals
from northeastern Mexico near the south
end of Don Martin Dam and the vicinity ofAllende,
Coahuila, and 3.2 km NW of Mina, Nuevo Leon,
have a gular coloration of yellow-orange surrounded
by olive green. Individuals to the south and west
(for example, 30 km SSW of Cuatrocienegas) have
the standard olive green gular coloration. Thus, it
appears that gular coloration grades smoothly from
yellow-orange to olive green in northeastern Mexico.
Fitch and Tanner (1 95 1 ) were the last to comment
extensively on the taxonomic status of C. c.
collaris and C. c. baileyi. They clearly recognized
the two as pattern classes and on these grounds accorded
them the rank of subspecies. With respect
to C. c. fuscus, diagnostic characters were not presented
in the type description, which was described
on the basis of a distinctive discriminant function
(Ingram and Tanner, 1971). Furthermore, Axtell
(1989~) suggested that C. c. jicscus, C. c. collaris,
and C. c. baileyi show three-way intergradation in
western Texas, again implying that all three are pattern
classes.
An additional problem with the current alpha taxonomy
of Crotaphytus collaris is that the paucity or
lack of adequate character support for the subspecies
makes it necessary to rely on color pattern diKerences
as a means of identification. Thus, although
it was not mentioned in the original description,
many herpetologists tend to think of C. c. baileyi as
a green collared lizard with a yellow head and C. c.
fuscus as a brown or grayish lizard (e.g., Stebbins,
1985; Conant and Collins, 199 I). Unfortunately, the