1 66 University of California Publications in Zoology 



7. Foramina in ventral surface of second sacral pleurapophyses usually absent; their 

 place taken by open grooves (58-B). This character exists as a polymorphism in both 

 species of Conolophus; that is, it does not characterize all specimens. 



8. Subclavian arteries not covered ventrally by M. rectus capitis anterior (76-B). This 

 character needs to be checked in additional specimens. 



Fossil record: Steadman (1981) reported Conolophus fossils of undetermined age from 

 a lava tube on Isla Santa Cruz, Galapagos. 



Etheridge (1964b) reported a fragmentary braincase and a body vertebra from Late 

 Pleistocene cave deposits on the West Indian island of Barbuda and estimated that both 

 were from animals about 400 mm snout-vent length. He stated that the body vertebra, with 

 its robust neural spine and well developed zygosphenes and zygantra, is similar to those of 

 large iguanines. Etheridge compared the braincase with those of various large iguanines 

 noting, as pointed out by Boulenger (1890), that the parabasi sphenoid "is much wider than 

 long and sHghtly to moderately constricted behind the [basi]pterygoid processes in Iguana 

 and Cyclura, about as wide as long and strongly constricted in Amblyrhynchus and 

 Conolophus, and much longer than wide and strongly constricted in Ctenosaura" 

 (Etheridge, 1964b:68). He also gave the following length-to-width ratios for the 

 parabasisphenoid (length measured from posterior border to apex of indentation between 

 basipterygoid processes, width measured at narrowest point posterior to basipterygoid 

 processes): Iguana .40-. 65, Cyclura .64-.72, Amblyrhynchus .79-.91, Conolophus .86- 

 1.10, Ctenosaura 1.45-1.96. Because the ratio of the fossil is 1.00, Etheridge concluded 

 that it most closely resembles Conolophus. 



Based on its large size and the presence of zygosphenes and zygantra, the vertebra is 

 reasonably interpreted as belonging to an iguanine. Based on size, both vertebra and 

 braincase might tentatively be referred to Iguanini, The similar proportions of the 

 parabasisphenoid in the fossil and Conolophus, however, provide no evidence that the two 

 are closely related. The wide parabasisphenoids of Iguana and Cyclura, and the long one 

 of Ctenosaura, are derived conditions, while Amblyrhynchus, Conolophus, and the fossil 

 retain primitive proportions of this element. Furthermore, the proportions of the 

 parabasisphenoid in the fossil fall within the range of variation not only of Conolophus but 

 also of Cyclura. Etheridge's (1964b) range of .64-. 72 for the length/width of the 

 parabasisphenoid in Cyclura is based on C. cornuta, C.figginsi (=cychlura), C. ricordii, 

 and C. macleayi (=nubila), but the range is actually much greater when other Cyclura are 

 included. Pregill (1981) reported a ratio of .50 for a Puerto Rican fossil that he referred to 

 C. pinguis, and I have obtained a range of .52 (C. pinguis) to 1.10 (C. carinata). Although 

 neither Conolophus nor Cyclura occurs on Barbuda today, Cyclura occurs in the West 

 Indies, while Conolophus is restricted to the Galapagos Islands. Nevertheless, current 

 knowledge does not permit me to refer the Barbuda fossil to either of these taxa. 



Comments: Although not as obviously modified from the ancestral Amblyrhynchina as 

 its sister taxon, Amblyrhynchus, Conolophus has eight derived characters not seen in 



