. Chordate morphology. Morphology (Animals); Chordata. pisiforme 1 calcified' fibula Figure 6-50. Manus and pes of Tupinambis, A and B, and Sphenodon, C and D. The structure of the carpus in the early reptiles is not clearly revealed, but a captorhinid and the pelycosaurs (Figure 6-51) are quite like Sphenodon. Seymouria appears to have had at least one centrale. The number of digits was five in these reptiles, and the phalangeal formula was 2-3-4-5-3. Among later reptiles, including the living types, a reduc- tion in the number of carpais or digits has occurred. The alligator lacks an interme
. Chordate morphology. Morphology (Animals); Chordata. pisiforme 1 calcified' fibula Figure 6-50. Manus and pes of Tupinambis, A and B, and Sphenodon, C and D. The structure of the carpus in the early reptiles is not clearly revealed, but a captorhinid and the pelycosaurs (Figure 6-51) are quite like Sphenodon. Seymouria appears to have had at least one centrale. The number of digits was five in these reptiles, and the phalangeal formula was 2-3-4-5-3. Among later reptiles, including the living types, a reduc- tion in the number of carpais or digits has occurred. The alligator lacks an intermedium and has only three distal elements. Carpais I and II tend to fuse, and carpais III and IV are joined from the beginning of ossification. The pisi- forme is much reduced. The ichthyosaurs had paddles or flippers like the whale and in these the number of phalanges is even greater than in the mammal—all five digits are in- volved in this polyphalangy. An extreme of the reptile type is observed in the bird, where the carpus includes only a radiale and ulnare and the digits are reduced to three. It has generally been as- sumed that the remaining digits were one, two, and three— a fourth vestigal digit was also known. Several embryologi- cal studies suggest that in fact the well-developed digits are two, three, and four, with five in a vestigial state. Pelvic appendage The pelvic girdle of the reptile as ob- served in Sphenodon or Tupinamhis has three elements nearly. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jollie, Malcolm. New York, Reinhold
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