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associated with the more elongate snout seen in this
species. This hypothesis is corroborated by the relatively
slender septomaxillae seen in C. bicinctores,
C. dickersonae, C. grismeri. C. insularis, and C. vestigiutn,
which also have relatively elongate snouts.
However, these taxa do not have the extreme condition
present in G. ~vislizeniiand G. copei. Elongate,
slender septomaxillae are rarely observed within Iguania.
In Oplurus (0. cuvieri and 0. qttadritnaculatus),
they are extremely slender, almost splinterlike,
while in certain other iguanians (Pltrynoson~a
asio, P. orbiculare, P. coronarurn, some Dipsosaurrcs
dorsalis) they are slender, although to a lesser degree.
Elongate, slender septomaxillae are considered to
be the derived state. However, septomaxillae are
often destroyed during the preparation of skeletons
and many outgroup taxa are not represented here.
Because this feature appears to be associated with
the much more elongate snout that occurs in G.
wislizenii and G. copei, this character is treated as
a character complex (although all of the differences
that appear to be associated with an elongate snout
cannot be polarized as can the septomaxillae conditions).
~Wavillae (Characters 12, 13; Fig. 2-5,7,8). -The
premaxillary process contacts the premaxilla anteriorly
by means of an overlapping sheet of bone. It
includes a well-developed shelf that passes posterior
to the nasal process of the premaxilla and acts as
the anterior wall of the external naris. The septomaxilla
contacts the posterodorsal edge of this shelf
while posteroventrally the shelf is contacted by the
vomer. In Gambelia rvislizenii, G. silrts, and five of
eight G. copei (absent in REE 2798, 2802, 2805), a
protrusion of the premaxillary process overlaps the
lateral edge of the premaxilla such that the suture
is saddle-shaped (Fig. 3-5). This condition is only
rarely observed in the outgroups (present in some
Cizalaradon madagascariensis, Petrosaurus nteartlsi,
Urostrophus vautieri, some Pristidactylzts torquatus,
Enyalius brasiliensis, E. pictus, Pizymaturus
punae, some P. pallttma, Leiocephalus melanoc~zlorus,
and some L. carinatus) and is considered to
be the derived state.
The dorsally directed nasal process of the maxilla
contacts the nasal, prefrontal, and lacrimal bones
and forms the posterolateral wall of the external
naris and the lateral wall of the nasal capsule. A
canthal ridge is present on the nasal process and
extends from the rugose protuberance of the prefrontal
to the base of the premaxillary process near
the posterolateral comer of the external naris. The
OF CROTAPHYTID LIZARDS 17
angle of the canthal ridge, as well as the posterior
margin ofthe external naris, is much greater (greater
than 45 degrees) in Crotapizytus, Gatnbelia coronat,
and G. silus than it is in G. ~vislizenii and G. copei
due to the elongate snout of the latter two species.
Several potentially useful characters are associated
with the longer snout of G. rvislizenii and G. copei,
including the more elongate septomaxillae and vo-
mers. However, as each of these appears to be linked
to rostra1 elongation, they are considered as one
character (see septomaxillae) in this analysis.
Ventromedially, a thickening of the maxilla forms
a shelf-like process that overlaps the palatine. This
shelf projects further medially in Crotaphytus (Fig.
11, 12) than in Gatnbelia and is more nearly tri-
angular. In Gatnbelia, the shape of the process is in
the form of a low, rounded arch. There is extensive
variation in the outgroups with regard to this feature
and it was left unpolarized.
Jugals (Characters 14, 15; Fig. 2-4, 8, 1 l).-The
general shape of the jugal varies little in crotaphytids
although three potentially useful variations were ob-
served. A ridge, or thickening, is found on the ex-
temal surface of the jugal, extending from its im-
mediate anterior end posteriorly just beyond the
jugal's articulation with the postorbital. The ridge
is thicker in Crotaphytus than in Gatnbelia and is
most developed in C. reticrtlatus. The function of
this ridge is uncertain, although it provides the sur-
face for attachment of the subocular scales. A lateral
ridge is present on the jugal in many iguanians, al-
though it is usually less strongly developed than that
of Crotaphytus. Although this may eventually prove
to be a phylogenetically useful character, it was not
considered in this analysis.
All crotaphytids possess an enlarged tubercle pos-
terior to the termination of the maxillary tooth row
(Fig. 2, 8, 11). This tubercle is actually comprised
of both the jugal, which forms the anterior portion,
and the ectopterygoid, which forms the posterior
portion. The function of the tubercle appears to be
as an attachment site for the ligamentum quadra-
tomandibulare. The size of the tubercle is interspe-
cifically variable, with Crotaphytus antiquu. C. col-
laris, C. dickersonae. C. nebrius, and C. reticulatus
having very large tubercles and the remaining taxa
having small ones. Despite this variation in size, the
presence or absence of a tubercle was coded as a
binary character. In the outgroups, a similar tubercle
is present in the leiosaurs Pristidactylus, Diplolae-
mus, and Leiosatrrus and a less similar laterally com-
pressed tubercle is present in some chamaeleonids