Reconstructing the palaeodiet of Florida Mammut americanum via low-magnification stereomicroscopy

Abstract

A large sample ( N = 76) of Pleistocene mastodon ( Mammut americanum) teeth from a variety of localities in Florida were analyzed for dental enamel microwear features via low-magnification stereomicroscopy. Second upper and lower molars were used for dental dietary reconstruction purposes to allow comparison of results to an extensive molar microwear database comprised of extant taxa with well-studied diets. Deciduous premolars and permanent molars were tested for consistency of enamel scar patterns. We used both Kruskal–Wallis and Mann–Whitney tests to test for differences across the tooth row in: (1) average pit frequency, (2) average scratch frequency, (3) scratch textural properties, and presence or absence of (4) gouges, (5) large pits, and (6) cross scratches. Of these variables, only the gouges showed significant between-tooth differences at p < .05. A Mann–Whitney test reveals that the anterior-most premolar (DP2) has significantly fewer gouges than do the other cheek teeth (especially the molars), but that there are no significant differences in gouging between any other pair of teeth. This difference may reflect ontogenetic dietary change but needs to be studied further. Stereoscopic microwear results were compared to an extant herbivore microwear trophic triangle representing average scratch and pit morphospaces for extant taxa, including graminivores, folivores, and frugivores. Enamel scar patterns for M. americanum for six microwear variables are consistent with a browsing diet but apparently one unlike that of typical extant browsing forms. Evidence for extensive bark consumption and some fruit consumption is presented. Cluster analysis reveals a clear segregation of M. americanum from typical extant browsing forms, from grazing or mixed feeding forms, and from extant African and Indian elephants. Euclidean distance comparisons reveal a dietary profile most similar to that of the extant Diceros bicornis (black rhino), a well-known browser with a prehensile lip that is used for gathering twigs into its mouth. Our results are consistent with reports for Florida mastodons showing a preponderance of twigs such as Taxodium (bald cypress) in preserved digesta.