Abstract
Unworn teeth of herbivorous mammals are not immediately functional. They have to be partially worn to expose enamel ridges which can then act as shear-cutting blades to break the food down. We use the Plains Zebra (Equus quagga) as a hypsodont, herbivorous model organism to investigate how initial wear of the tooth crown is controlled by underlying structures. We find that the enamel proportion is smaller at the apical half of the tooth crown in all upper tooth positions and suggest that lower enamel content here could promote early wear. Besides this uneven enamel distribution, we note that the third molar has a higher overall enamel content than any other tooth position. The M3 is thus likely to have a slightly different functional trait in mastication, resisting highest bite forces along the tooth row and maintaining functionality when anterior teeth are already worn down.
Highlights
Hypsodonty has been defined as the relative increase in the height of cheek teeth (Van Valen, 1960), or more as larger tooth crown height compared to tooth crown length (White, 1959; Thenius, 1989; compare Fig. 1)
Though distribution of enamel content per section was variable between teeth, it was consistently smallest in Section 1 for all tooth positions when total volume was considered
The results of this study support our hypothesis that the apex of the tooth crown is structurally different from the rest of the tooth
Summary
Hypsodonty has been defined as the relative increase in the height of cheek teeth (Van Valen, 1960), or more as larger tooth crown height compared to tooth crown length (White, 1959; Thenius, 1989; compare Fig. 1). It is a common evolutionary strategy of herbivorous mammals to counter high abrasive loads in the ingested diet, which result in a high degree of dental wear. More often such empty chewing is considered a behavioural anomaly
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