Studies of paleoenvironments have commonly focused on large mammalian herbivores such as ungulates. Many localities, however, have yielded large numbers of small mammalian herbivores, including lagomorphs and rodents. These fossils represent an untapped paleoecological resource. However, the fossils are often in the form of isolated teeth, and microwear analysis cannot be used due to taphonomic alteration. As a result, we use ungulate gross dental wear as a model. The dental wear features of extant western Canadian lagomorphs are identified and used to create dietary categories that can be applied to make predictions about the diets of extinct forms. The Horse Local Fauna of the Cypress Hills Formation of Saskatchewan has yielded approximately 2,500 fossil specimens, of which nearly 300 are lagomorphs. Two leporid species (rabbits and hares) are present in the Horse Local Fauna, Palaeolagus temnodon and Megalagus brachyodon. Qualitative analysis of the gross dental wear of the lagomorphs of the Horse Local Fauna indicates that M. brachyodon was mainly folivorous and P. temnodon was primarily frugivorous, suggesting that the contemporaneous ecosystem was tree dominated. Gross dental wear analysis allows the use of small herbivores and isolated teeth in paleoecological studies. Studying the diets of small herbivorous mammals will allow more nearly complete reconstructions of past environments and will become increasingly important as more detailed reconstructions are required by paleontologists.