SPATIAL AND TEMPORAL VARIABILITY IN NORTH AMERICAN GOMPHOTHERE DIET AS INFERRED FROM DENTAL MICROWEAR TEXTURES

Dental microwear, the microscopic features on mammalian wear facets that form during food processing, can be an informative means for reconstructing the textural properties of foods consumed by extinct organisms. Over the past few decades, microwear has been used extensively to understand the dietary preferences of extinct proboscideans, including mammoths and mastodons. While the dietary ecologies of these taxa are well-understood, gomphothere diets are less understood and more variable; populations of different ages and locations often display varying dietary preferences. Further, most dental microwear analyses on gomphotheres come from South America or Europe; therefore, North American gomphothere dietary ecology remains poorly resolved.

To assess North America gomphothere dietary variability through space and time, we analyzed the dental microwear textures from over 150 gomphothere specimens from both Florida and Texas. Taxa include Gomphotherium, Gnathabelodon, Stegomastodon, Rhychotherium, and Cuvieronius and span a period of approximately 16 million years (from the Barstovian through Rancholabrean land mammal ages). Results demonstrate the consumption of both tough and hard food items through time and by all taxa examined, with subtler (but significant) differences between heterogeneity of wear surfaces in Gnathabelodon and Gomphotherium, Cuvieronius and Gnathabelodon, and Rhychotherium and Stegomastodon. Additionally, the mixed-feeding Gomphotherium had significantly greater anisotropy than the browsing Rhychotherium, suggesting nuanced differences in dietary preferences in gomphothere taxa.

Along with a depauperate fossil record and limited paleogeographic range during the Pleistocene, these results suggest that gomphotheres consumed a wide range of resources and were not specialized on either grasses or browse - but rather consumed a mixture of food resources with variable textural properties. Their potential "jack of all trades and master of none" feeding strategy may have proved challenging when competing with the primarily browsing mastodons and grazing/mixed feeding mammoths, leading to the early extirpation of the gomphothere from North America.