. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. Axial Skeleton of Chamaelinorops • 293 ribs articulate with the parapophyses of vertebra no. 8, which are similar to those of the thoracic vertebrae, and conse- quently the capitulum size and average shaft diameter of each of the posterior pair of cervical ribs are much closer to that of the thoracic ribs than to that of the anterior cervical ribs. Each of the anterior two pairs of cervical ribs bears a small, flat, triangular proce
. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. Axial Skeleton of Chamaelinorops • 293 ribs articulate with the parapophyses of vertebra no. 8, which are similar to those of the thoracic vertebrae, and conse- quently the capitulum size and average shaft diameter of each of the posterior pair of cervical ribs are much closer to that of the thoracic ribs than to that of the anterior cervical ribs. Each of the anterior two pairs of cervical ribs bears a small, flat, triangular process on its lateral sur- face, with the point of the triangle direct- ed posterolaterally (see Fig. 5). The cartilaginous tips of the anterior two pairs of thoracic ribs in Chamaelin- orops articulate directly with the ster- num. The third, fourth, and fifth pairs of thoracic ribs articulate indirectly with the sternum via a cartilaginous xiphistemum. This sternal: xiphisternal formula of 2:3 in the one specimen examined is counter to the claim of Etheridge (1960) that all anolines except Phenacosaurus (2:2) have a formula of 3:2. The sixth, seventh, eighth, and ninth pairs of thoracic ribs are. Figure 5. Ribs and inscriptional ribs of Chamaelinor- ops (schematic) (MCZ 146960). attached inscriptional ribs, with each pair meeting at the midventral line to form an anteriorly directed cartilaginous chevron. Posterior to the cartilaginous chevron of the ninth thoracic rib pair is one free inscriptional rib chevron, which does not extend to the ventral ends of the cartilagi- nous tips of the bony elements of the tenth pair of thoracic ribs, to which it cor- responds. This fixed-chevron to floating- chevron ratio of 4:1 in the one specimen examined differs from the ratios of 4:2 and 3:3 reported for Chamaelinorops by Etheridge (1965), indicating that intra- specific variation in that ratio may not be as conservative as he asserted. The ribs of the eleventh thoracic pair are the short
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Keywords: ., bookauthorharvarduniver, bookcentury1900, booksubjectherpetology
