. Bulletin of the Southern California Academy of Sciences. Science; Natural history; Natural history. Notes on killer whales 135. Figure 5. Ventral view of the Newport killer whale. Photograph by \\. K Aloiia- han, Marineland of the Pacific. related as a cause for the extreme tooth wear or for the death of the animal. Rather than the obvious explanation that such wear as evidenced by the Newport specimen is a simple wearing down of the apices of the teeth, the factors accounting for such extreme wear, assuming it was not the result of injury to the jaw, might be more complex. For example: firs
. Bulletin of the Southern California Academy of Sciences. Science; Natural history; Natural history. Notes on killer whales 135. Figure 5. Ventral view of the Newport killer whale. Photograph by \\. K Aloiia- han, Marineland of the Pacific. related as a cause for the extreme tooth wear or for the death of the animal. Rather than the obvious explanation that such wear as evidenced by the Newport specimen is a simple wearing down of the apices of the teeth, the factors accounting for such extreme wear, assuming it was not the result of injury to the jaw, might be more complex. For example: first, the typical interlocking action of the incurved teeth results in wear on their anterior and posterior faces (Fig. 1), brought about by vertical movements of the jaws. Second, direct op- position during vertical, lateral and palinal movements of the jaws results in some grinding wear on the apices of the teeth (Fig. 2). Third, the horizontal grooving, apparently caused by the palinal movement of the opposing teeth past one another, eventually could result in a serious undercutting effect (Fig. 2). The point of this un- dercutting is near the gum line (see Caldwell, et al., 1957: fig. 3; Fig. 2 herein). Such undercutting may occur on both the labial and lingual sides of the tooth (see Figs. 1 and 2, especially the third, sixth and eighth teeth from the right in Fig. 2), permitted by the varied lateral positions of the free-moving opposing lower jaw. Combining these patterns of wear, which all must occur in a normally active individual, the result eventually would be the condition exhibited by the Newport animal. The tooth wear in the San Miguel Island specimen indicates that the progression of wear essentially is from anterior to posterior, although the wear on the teeth of other speci- mens suggests that there is some variation in this. The above combi- nation of wear patterns and resulting progression of wear was sug- gested from our study of the series of specimens examined
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