Three-dimensional reconstruction of tooth relationships during carnivoran chewing

Contact between teeth during chewing has often been studied using the indirect evidence of cinematography during chewing and the wear facets on teeth. However, neither by itself gives the entire picture of the occlusal relationships between teeth. Here, we endeavoured to relate the two different lines of evidence using three-dimensional reconstructions of tooth-tooth contact in eight carnivoran species based on the shape of teeth and jaw joints. We found that jaw movement generates contacts between teeth that are consistent with attrition wear facets. This supports the long-held but not fully verified view that attrition facets are generated by tooth-tooth contact during chewing. The second major issue investigated was the shape of attrition facets on teeth. It has generally been assumed that such facets are planar. Here we establish that many attrition facets in carnivoran teeth are not planar. Non-planar attrition facets can, in fact, improve functional characteristics of the teeth such as relief behind occluding blades. We also show how the three-dimensional shape of facets affects the occlusal path of the teeth, which was found to be non-linear in carnivorans. Four morphological groups of carnivorans were examined. It was found that the degree of lateral movement in the chewing cycle was positively related to the number and complexity of the teeth in the tooth row.