CONCLUSION

The mandibular robustness of ungulate jaws appears to be reliably correlated with digestive physiology in a range of extant species and potentially also in extinct species. In general hindgut feeders have jaws which show lower levels of stress when equal muscle forces are applied in FEA analysis (i.e., are more "robust"), and these jaws can be significantly differentiated from the relatively more gracile jaws of ruminants, especially when the species are matched for body mass and dietary type. This observation accords with the greater amount of stress predicted for hindgut fermenters due to their relatively greater levels of food ingestion and mastication.