The evolution of high-crowned molars among horses (Family Equidae) is thought to be an adaptation for abrasive diets associated with the spread of grasslands. The sharpness and relief of the worn cusp apices of teeth (mesowear) are a measure of dietary abrasion. We collected mesowear data for North American Equidae for the past 55.5 million years to test the association of molar height and dietary abrasion. Mesowear trends in horses are reflective of global cooling and associated vegetation changes. There is a strong correlation between mesowear and crown height in horses; however, most horse paleopopulations had highly variable amounts of dietary abrasion, suggesting that selective pressures for crown height may have been weak much of the time. However, instances of higher abrasion were observed in some paleopopulations, suggesting intervals of stronger selection for the evolution of dentitions, including the early Miocene shortly before the first appearance of Equinae, the horse subfamily in which high-crowned dentitions evolved.

The Brontotheriidae is an extinct family of Eocene perissodactyls known from North America, Asia, and, rarely, Eastern Europe. Brontotheres are widely recognized as having evolved very large body size and conspicuous frontonasal horns, although these traits do not characterize every species. Characters shared by all brontotheriids include an anteroposteriorly abbreviated face and an elongate postorbital cranium. Dentally, brontotheriids share bunoselenodont upper molars with a W-shaped ectoloph, isolated lingual cusps, and with paraconules, metaconules, and transverse molar crests that are either vestigial or absent. Early North American paleontologists such as Leidy, Cope, Marsh, and Osborn placed considerable emphasis on brontothere research, however, since Osborn's massive 1929 monograph on North American brontotheres, serious research on this diverse Eocene family has waned. Nonetheless, a great need for a revision of the Brontotheriidae has long been recognized because earlier works on brontothere taxonomy and systematics, particularly those of Osborn, are universally considered problematic due to their reliance on the discredited theory of orthogenesis.

During the late Pleistocene and early Holocene, Bison was widely dispersed across North America and occupied most regions not covered by ice sheets. A dietary study on Bison paleopopulations from Alaska, New Mexico, Florida, and Texas was performed using two methods that relate dental wear patterns to diet, mesowear analysis and microwear analysis. These data were compared to a mixed sample of extant Bison from the North American central plains, extant wood Bison from Alberta (Canada) and a variety of other modern ungulates. Mesowear relates macroscopic molar facet shape to levels of dietary abrasion. The mesowear signature observed on fossil Bison differs significantly from the hyper-abrasive grazing diet of extant Bison. Tooth microwear examines wear on the surface of enamel at a microscopic scale. The microwear signal of fossil samples resembles to modern Bison, but the fossil samples show a greater diversity of features, suggesting that fossil Bison populations regularly consumed food items that are texturally inconsistent with the short-grass diet typical of modern plains Bison. Mesowear and microwear signals of fossil Bison samples most closely resemble a variety of typical mixed feeding ungulates, all with diets that are substantially less abrasive than what is typical for modern plains Bison. Furthermore, statistical tests suggest significant differences between the microwear signatures of the fossil samples, thus revealing geographic variability in Pleistocene Bison diets. This study reveals that fossils are of value in developing an understanding of the dietary breadth and ecological versatility of species that, in recent times, are rare, endangered, and occupy only a small remnant of their former ranges.