. Bulletin of the British Museum (Natural History), Geology. CYNODONTS AND TRITYLODONTIDS 37 the later forms a fresh supply of teeth with deep shearing planes were added. In gomphodonts the enamel covering the crowns of the teeth appears to have been thin and perhaps soft, so that the structure of the crown was soon worn away and the teeth were perhaps replaced more rapidly than in mammals. The exact order of tooth replacement occurring in the ontogeny of Diademodon is not fully understood; it is hoped that further work on material already available will clarify this process and meet the objec


. Bulletin of the British Museum (Natural History), Geology. CYNODONTS AND TRITYLODONTIDS 37 the later forms a fresh supply of teeth with deep shearing planes were added. In gomphodonts the enamel covering the crowns of the teeth appears to have been thin and perhaps soft, so that the structure of the crown was soon worn away and the teeth were perhaps replaced more rapidly than in mammals. The exact order of tooth replacement occurring in the ontogeny of Diademodon is not fully understood; it is hoped that further work on material already available will clarify this process and meet the objections raised by Dr. Ziegler. Crown views of unworn upper and lower gomphodont teeth of Diademodon are given in Fig. 3A and Plate 2. The upper crowns were transversely ovate whereas the lower crowns tended to be more circular. The upper crown was dominated by an external main cusp from which a well-defined ridge ran directly forwards, bearing two or three subsidiary cups which became smaller towards the front; another ridge, ill-defined and slightly crenulate, ran backwards from the tip of the external main Sh. I cm Fig. 3. Diademodontids and trirachodontids. Postcanine teeth. A. Diademodon. Crown view of typical upper and lower gomphodont teeth. B. Diademodon. Crown views of last five uppers and last four lowers to show shearing surfaces produced by wear. C. As in B, but superimposed as when occluded. D. As in C, occluded, but in internal view. E. Cricodon. Crown views of typical upper and lower. For key to abbreviations .see p. 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 British Museum (Natural History). London : BM(NH)


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