. The Canadian field-naturalist. 1984 Notes 507. Figures. Cleaned skull showing lesion and extent of bone erosion on lower jaw and the amount of curvature in both upper and lower incisors. The width of the lower left incisor has thinned uniformly from the base to the tip. The width of the base, measured at the alveolus, is mm, at mid- point mm, and at the tip mm. The upper left incisor has uneven thinning. The base measured mm at the alveolus. At a point approximately mm from the tip of the upper right incisor, the left incisor width measured mm, at mid-point it me
. The Canadian field-naturalist. 1984 Notes 507. Figures. Cleaned skull showing lesion and extent of bone erosion on lower jaw and the amount of curvature in both upper and lower incisors. The width of the lower left incisor has thinned uniformly from the base to the tip. The width of the base, measured at the alveolus, is mm, at mid- point mm, and at the tip mm. The upper left incisor has uneven thinning. The base measured mm at the alveolus. At a point approximately mm from the tip of the upper right incisor, the left incisor width measured mm, at mid-point it mea- sured mm, and at the tip mm. The thin part could be the result of wear by the lower right incisor if the squirrel deliberately moved the lower jaw toward the left to compensate for the irritation to the left eye caused by the lower left incisor. In the referred specimen the tips of the occluding incisors (the right side incisors) are blunted indicating that normal wear is not occurring (Figure 2), except for a small notch in the upper right incisor where the lower right incisor has made contact. The left upper incisor appears to be almost a com- plete circle (Figure 3). The tip has met, but not pene- trated, the maxillary bone. It is also touching P4 and appears to have been deflected toward the left by this tooth. The pressure of the incisor on the maxillary bone has caused the root portion of the tooth to rupture the socket wall so that the posterior portion of the incisor has intruded into the nasal chamber. The turbinal bones in the nasal chamber are damaged, probably caused by the intruding tooth although this may have occurred during the cleaning process. Had this individual continued to live it is probable that the lower incisor would have penetrated the left eye, as the tip of the tooth was already touching the eyeball. It is also likely that the upper incisor would have penetrated the maxillary bone. Even if either of these events did not cause death, the
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