. Breviora. 12 BREVIORA No. 399. Figure 7. Tracings of the jaws and postcanine dentitions from one side of all specimens except I, M, and N for which suitable photogi-aphs were not available. The tracings have been arranged in accordance with the growth processes suggested in Fig. 1. tion. Thus, although Thrinaxodon was strictly polyphyodont (because the dental lamina was active in budding new teeth through the life of the animal) the number of replacement teeth was severely limited when compared with most modern reptiles which have been studied. The following argument suggests that Thrinaxodo
. Breviora. 12 BREVIORA No. 399. Figure 7. Tracings of the jaws and postcanine dentitions from one side of all specimens except I, M, and N for which suitable photogi-aphs were not available. The tracings have been arranged in accordance with the growth processes suggested in Fig. 1. tion. Thus, although Thrinaxodon was strictly polyphyodont (because the dental lamina was active in budding new teeth through the life of the animal) the number of replacement teeth was severely limited when compared with most modern reptiles which have been studied. The following argument suggests that Thrinaxodon may have been evolving towards a condition in which the activity of the dental lamina terminated during the life of the animal. This is the characteristic which distinguishes polyphyodont from other dentitions. In the anterior postcanine tooth positions the last replacement teeth were so small (position 3 in dentitions D to K; position 4 in dentitions L to N) that they can hardly have had any functional value. Thus, it can be argued that, despite its continued presence, the dental lamina in these positions no. 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 Harvard University. Museum of Comparative Zoology. Cambridge, Mass. , Museum of Comparative Zoology, Harvard University
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