Advances in the reconstruction of extant ungulate ecomorphology with applications to fossil ungulates

Microwear analysis has been severely underutilized as a dietary technique due to numerous constraints involved in employing traditional scanning electron microscopy. A new methodology is described that greatly simplifies the assessment of microwear scar features for the discernment of the trophic adaptations of living and fossil taxa. A standard stereomicroscope and a fiber-optic light source have replaced specimen preparation tools such as venting and plating apparatus and the high-tech scanning electron microscope. Several new microwear variables supplement traditional quantification of pits and scratches. Significant niche partitioning in extant browsers, grazers, and mixed feeders is apparent and habitat differences within each broad trophic group are discernible by scoring relative pit sizes, scratch textures, and gouges in addition to quantifying scratches and pits.; Variations in scratch number ranges, scratch textures, and relative pit sizes are the most useful variables for partitioning living ungulates into more refined trophic categories. Pit numbers and scratch textures are most effective for distinguishing fine versus coarse browsing, as well as leaf browsing versus fruit browsing. Scratch textural differences and scratch numbers distinguish fresh grass grazing versus coarse or mixed grass grazing; C3 versus C4 grazing, coarse bark and stem feeding, and seasonal or regional mixed feeding versus a meal-by-meal alternation between browse and grass. Heavy gouging is used to distinguish significant grit encroachment upon food items. Seasonal or regional mixed feeders have microwear that is more similar to browsers, whereas meal-by-meal mixed feeders have wear more similar to grazers.; Three trophic phases are identified within extant ungulates by partitioning taxa into three potential raw scratch ranges: traditional browsing and grazing phases, comprised by surprisingly few species, and a browsing-to-grazing transitional phase where the majority of taxa are found, including all of the mixed feeders. The new microwear methodology is used to test two hypotheses regarding large shifts in dietary strategies in fossil ungulates from the North American Great Plains region: the supposed browsing-grazing transition in the fossil record of North American equids and the supposed shift to coarser browse in the fossil ruminant artiodactyl family known as the Dromomerycidae.