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McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS
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Fig. 7.-Dorsal view of the anterior portion of the skull of Cro-
raphytusgrismeri (MZFC 665 1, adult male, SVL = 92 mm). The
vertical hatching denotes the cxtn frontonasal bone present in
two of five specimens examined. Fro = frontal, Max = maxilla,
. . Nas = nasal, Prf = prefrontal, Prm = premaxilla. Scale = 5 mm.
Fig. 6.-Anterior portion of the orbit showing contact of the
prefrontal and jugal bones (Croraphytus dickersonae, adult male.
REE 2777, SVL = 116 mm). Jug = jugal, Lac = lacrimal, Max
= maxilla, Pal = palatine, Prf = prefrontal. Scale = 2 mm.
therefore, for the entire Tropiduridae. Because B.
stump@ and U. acanthinurus are the only nontro-
pidurid iguanian taxa examined here in which the
nasals overlap the nasal process of the premaxilla,
it is most parsimonious to code extensive overlap
of the nasal process by the nasals as the derived
state.
Pre/i.ontals (Character 4; Fig. 2-4, 6, 7).-In all
crotaphytids, the palatine process of the prefrontal
broadly contacts the jugal just posterior to the lac-
rimal foramen (de Queiroz, 1987; Fig. 6). This con-
dition was observed in Phrynosoma asio, Utna esul,
U. inornata, U. notata, U. scoparia, some Pltyma-
turus patagonicus payuniae, one of three Leioce-
phalus macropus. Microlophus grayi, one of three
Uranoscodon superciliosus, some Pristidactylus tor-
quatus, Polychrus acutirostris, and some Po. mar-
moratus. In Phrynosoma asio and L'ma (as well as
other sand lizards), this contact appears to be as-
sociated with loss of the lacrimal bone, which usu-
ally separates the prefrontal from the jugal in other
iguanians. The contact of the prefrontal and jugal is
considered to be the derived state and, thus, rep-
resents a synapomorphy for Crotaphytidae.
Although Norell (1989) stated that crotaphytids
can be diagnosed by the derived loss of the pre-
frontals, clearly (as he stated elsewhere in the paper),
he was referring to the loss of the postfrontals.
Frontal (Character 5; Fig. 2-4,7,8).-A separate,
median frontonasal bone (Fig. 7) is present in two
of five Crotaphytus grismeri (MZFC 6650, 665 1).
Although the sample size is small for this taxon, its
presence in two specimens suggests that it is a poly-
morphism rather than an aberration. A similar bone
was observed only in one Phymaturuspallurna (REE
23 13). Although this feature sheds no light on the
phylogenetic relationships within Crotaphytus, it
appears to represent an additional autapomorphy
for the species.
The skulls of Gambelia \vislizenii, G. copei, and
G. coronat are more depressed than those of Cro-
taphytzcs and G. silus. Although this variation ap-
pears to be associated with several bones, it is per-
haps best illustrated by comparing the shape and
orientation of the frontal bone. In Crotaphytus and
G. silus, this bone is more strongly convex, while in