126 University of California Publications in Zoology 



Three fully resolved cladograms of equal and minimum length can be constructed from 

 the 26 characters used in the lower-level analysis (Fig. 49). These cladograms differ only 

 in the position of Ctenosaura, which in turn depends on the interpretation of character 57, 

 the presence or absence of posterolaterally directed processes on the pleurapophyses of the 

 second sacral vertebra. The derived absence of these processes occurs in Ctenosaura, 

 Iguana, and some Cyclura, but was scored absent for the latter taxon in order to simplify 

 analysis. This is one of only two derived characters out of the set of 26 that occurs 

 invariably in Ctenosaura and is relevant to the placement of this taxon within the restricted 

 ingroup. The only other derived character that occurs invariably in Ctenosaura (character 

 23-B) also occurs in all ingroup taxa except some Sauromalus. Therefore, provided that 

 Sauromalus is monophyletic, this character is most reasonably interpreted as a 

 synapomorphy of the entire ingroup that has reversed in some Sauromalus. If the sister- 

 group relationship between Iguana and Cyclura, based on other characters, is accepted, 

 then character 57-B might be interpreted as convergent in Iguana on the one hand and in 

 Ctenosaura on the other. If so, Ctenosaura can have any of the relationships illustrated in 

 Figure 49; given this information alone, there is no reason to prefer any one of these 

 alternative placements over the others. Alternatively, character 57-B might be interpreted as 

 a synapomorphy of a clade consisting of Ctenosaura, Iguana, and Cyclura that has 

 subsequendy reversed within Cyclura. Because Cyclura is actually variable for this 

 character, the hypothesis of acquisition and reversal requires fewer phylogenetic 

 transformadons than does that of convergence (two instances versus three). Although one 

 of the three cladograms (Fig. 49A) would be favored under such an interpretation, the 

 difference is so small that little importance can be attached to it in terms of resolving the 

 placement of Ctenosaura. Therefore, I consider the relationships of Ctenosaura within the 

 restricted ingroup to be uncertain. 



Because the three minimum-step cladograms resulting from the lower-level analysis 

 differ only in the placement of Ctenosaura, I present diagnostic synapomorphies for a 

 single consensus cladogram (Adams, 1972) that leaves the relationships of Ctenosaura 

 unresolved (Fig. 50). This consensus cladogram is identical to the other three in terms of 

 evolutionary steps, requiring 37 phylogenetic character transformations out of the absolute 

 minimum of 26 (C-index = 0.70), which would only obtain if all characters had compatible 

 distribudons among basic taxa. The consistency indices (Kluge and Farris, 1969) for the 

 characters on the consensus cladogram (Fig. 50) are identical to those on the three 

 minimum-step cladograms (Fig. 49A,B,C) from which it was derived. These are given in 

 Table 9. Synapomorphies for the nodes of the consensus cladogram (Fig. 50) are given 

 below, with convergent characters underlined and characters involving reversal marked 

 with an asterisk. 



Node 1: 23-B*; Node 2: 37-B, 52-A; Node 3: 5-B, 7-B, 8-B, 17-B or-C, 21-B, 36-B 

 or-C, 40-B, 45-B, 50-B, 83-B; Node 4: 19-B, 28-B or-C, 39-B, 46-C or-D ; 

 Amblyrhynchus: 18-A . 54-B . 65-B . 68-B . 69-B . 70-B . 71-B . 84-A : Conolophus: none; 

 Ctenosaura: 57-B ; Cyclura: none; Iguana: 18-A , 57-B ; Sauromalus: 23-A*, 46-C . 54-B , 

 65-B . 68-B . 69-B . 70-B . 71-C . 84-A . 



