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1996 McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 2 7 (Fig. 16). They were separated in one of four C. antiquus, in all specimens of G. copei and G. silus, and in at least ten of 15 G. wislizenii. However, in those five specimens of G. wislizenii in which the second ceratobranchials were in contact, the contact may have been an artifact of preparation. Separated second ceratobranchials are relatively rare in igu- anians and were only observed in Uta stansburiana, some Petrosaurus mearnsi, Phrynosoma asio, some Uma exsul, some Brachylophus fasciatus. Phyma- turus, some Leiolepis belliana, and Enyalius bilineatus. Separated second ceratobranchials was considered to be the derived state within Crotaphytidae. However, this character could not be evaluated in many outgroup taxa because the hyoid apparatus is often damaged in preparation and this polarity as- sessment should only be considered tentative. SkuN Rugosity (Character 37). -Rugosity of the skull was considered to be a synapomorphy for Cro- taphytus by Frost and Etheridge (1989). Although rugosities may indeed be found in all Crotaphytus taxa (rugosities are not found in Gambelia), there is much variation with respect to the ontogenetic pe- riod during which rugosities develop. For example, most C. collaris develop rugosities as subadults, while C. bicinctores, C. dickersonae, and C. nebrius con- sistently develop rugosities only after reaching adult size. In C. grismeri, C. insularis, C. reticulatus, and C. vestigium, rugosities may be lacking even in large adults. For example, an extremely large C. vestigium (REE 2935; SVL = 125 mm) completely lacks skull rugosity, while several much smaller individuals have them. This variation was coded as a binary character with the absence of skull rugosity as state 0, and the presence of skull rugosity at some point in ontogeny as state 1. This character could not be polarized. Axvu. SKELETON Presacral Vertebrae (Character 38).-The presacral vertebrae of crotaphytids are procoelous and have supplemental articular facets, zygosphenes and zygantra, medial to the pre- and postzygapophyses. A large posterodorsally oriented suprazygapophy- sial process is present on the atlas. Crotaphytids retain the apparently plesiomorphic mode of eight cervical vertebrae and 24 presacral vertebrae, although individuals occasionally have nine cervicals and more frequently may have 23 or 25 total pre- sacrals. Four to seven ventrally keeled intercentra - - Fig. 16.- Hyoid skeletons of (A) Crofaphy~uscollaris (REE 2952, adult male, SVL = 131 mm), (B) C. dickersonae (REE 2905, adult male, SVL = 106 mm), and (C) Gambelia copei (REE 2800, adult female, SVL = 123 mm). B = body ofhyoid, Bh = Basihyal, Cbl = first ccntobranchial, Cb2 = second ceratobranchial, Ch = Ccratohyal, Hh = hypohyal. Scale -- 10 mm. occur between the anteriormost cervical vertebrae and these decrease in size posteriorly. The zygosphenes and zygantra of all crotaphytid taxa except Gambelia silus are weakly to moderately developed, according to the criteria established by Hoffstetter and Gasc (1969) and modified by de Queiroz (1987). In the weak form, the facet of the zygosphene faces dorsolaterally, while in the moderately developed form, the facet faces either laterally or ventrolaterally. The most strongly developed form of zygosphene is characterized by a ventrolaterally facing facet with a notch separating this facet from the prezygapophysis. This condition is approached in four of five G. silus, in which either a notch is present or a very thin sheet of transparent bone fills the space. Although notched zygosphenes are present in several of the outgroup taxa, including corytophanids, iguanids exclusive of Dipsosauncs, Uranoscodon superciliosus, Polychrus marmoratus, and some Enyalius (E. boulengeri, E. bilineatus), the condition of G. silus is considered to be the derived state within Crotaphytidae. Caudal Vertebrae (Characters 39,40).-The number of caudal vertebrae present in crotaphytids is remarkably consistent with all of the species having between 54 and 63. No gaps were obser-ved sug- gesting that the number of caudal vertebrae is not phylogenetically informative within Crotaphytidae. Most of the caudal vertebrae bear neural arches, transverse processes, and haemal arches, all of which
28 BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32 decrease in size posteriorly and disappear before the caudal terminus. The first haemal arch or rudirnen- tary haemal arch usually occurs between the second and third or third and fourth caudal vertebrae, although it may occasionally lie between the first and second caudal vertebrae. The number of transverse processes is highly variable. Relatively few transverse processes are present in C. insularis (14-1 8, R = 16.6), C. grismeri (1 6-22, X = 18.0), G. silus (14-24+, R = 1 LO), G. wislizenii (13-26, X = 18.4), C. aniiquus (19-22, 2 = 20.3), C. vestigium (17-30, = 2 1.3), C. bicinctores ( 16-26, R = 2 1.9), and G. copei (1 7-26,X = 23.3), while an intermediate number is present in C. dickersonae (24-35, R = 28.6), and a relatively large number are found in C. reticulatus (29-38, X = 33.4), C. nebrius (2342, X = 34.9), and C. collaris (27-47, R = 37.4). These num- bers may be complicated by ontogenetic variation as juveniles tended to have fewer transverse processes than adults. Although the data presented here are suggestive, the extensive interspecific overlap in ranges prevented the assignment of discrete character states for each taxon. Therefore, this variation was not considered in the phylogenetic analysis. In many iguanian lizards, the transverse processes of the more anterior caudal vertebrae project pos- terolaterally but abruptly change to an anterolateral orientation over the span of a few vertebrae (Eth- eridge, 1967). As Etheridge (1 967) pointed out, this condition is present in crotaphytids, although in two taxa unavailable to Etheridge at the time, C. grismeri (five of five) and C. insularis (four of five), this change in orientation usually does not occur. The shift in orientation did not occur in seven of 15 C. bicinctores, one of four C. anliquus, one of 15 C. dickersonae, three of 2 1 C. vestigium, and four of 2 1 G. wislizenii. The ranges and means for the caudal ver- tebra number at which the shift in orientation of the transverse processes occurs for each taxon follows: C. antiquus (8-1 5, R = 10.7), C. dickersonae (8-12, n = 1 1.3), C. insularis (I 2), C. nebrius (1 0-1 7, .t = 12.5), C. collaris(l0-18, L= 13.3), G. silus(13-16, X = 14.2), C. vestigium (9-22,X = 14.3), G. wislizenii (1 3-18, R = 15.4), C. reticulatus (14-20, R = 16. l), G. copei (1 6-23, R = 17. I), and C. bicinctores (1 7- 23, R = 19.9). Again, the extensive interspecific overlap in ranges limits the phylogenetic usefulness of this variation and it was not considered in the phylogenetic analysis. Adult male C. bicinctores, C. dickersonae, C. grismeri, C. insularis, and C. vestigium are characterized by the presence of a strongly laterally compressed tail (Fig. 3 lB, 32A-D). In each of these species, the tail is not only compressed, but relatively taller than in other crotaphytids and this is reflected in the morphology of the caudal vertebrae. The neural and haemal arches are relatively longer and the transverse processes narrower. In the species with strongly compressed tails the neural spines are approximately 2.0-3.0 times longer than the transverse processes while in the remaining species of Crotaphytus and in Gambelia, the neural spines are shorter than the transverse processes, approximately equal in length, or, in the case of C. reticulatus, approximately 1.5 times longer than the transverse processes. The tail of C. reticulatus may be weakly laterally compressed. However, the tail is never compressed to the degree observed in the species men- tioned above and in some individuals may not be compressed at all. Furthermore, the height of the laterally compressed tail of the other species is en- hanced by the presence of large fat bodies on the dorsal and ventral crests of the tail. These large fat bodies are not present in C. reticulatus or any other crotaphytid, although I have observed a minute line of fat on the dorsal surface of the tail of one C. collaris. Although several anatomical systems have been modified to produce the lateral tail compression of C. bicinctores, C. dickersonae, C. grismeri, C. insularis, and C. vestigium, these modifications are clearly associated with one complex character and are treated as such in this analysis. Although lateral tail compression occurs in several iguanian families, I have not observed similar fat bodies in the tails of these taxa. Therefore, lateral tail compression with the presence of dorsal and ventral fat bodies is considered to be the derived state within Crotaphytidae. Autotomic fracture planes of the caudal vertebrae are widespread in squamates and rhynchocepha- lians and at the level of Iguania certainly represent a plesiomorphic retention (Etheridge, 1967; Hoffs- tetter and Gasc, 1969). While fracture planes are present in most Gambelia, fracture planes are absent from Crotaphyt us (Etheridge, 1967). Fracture planes were present in five of five G. silus and seven of ten G. copei (and apparently fused in the remaining three). Fracture planes were present in 19 of 23 G. wislizenii; however, the four that lacked them were the only four specimens available from Isla Tiburon and, thus, may represent a derived feature for this insular population. Many iguanian taxa lack auto-
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