DIETS OF NOTOUNGULATES FROM THE SANTA CRUZ FORMATION, ARGENTINA:
NEW EVIDENCE FROM ENAMEL MICROWEAR
K. E. Beth Townsend and Darin A. Croft, Journal of Vertebrate
Paleontology, 2008, 28(1):217–230
The late early Miocene Santa Cruz Formation of Patagonian Argentina is remarkable for its wellpreserved and diverse mammalian fauna. This study evaluates the feeding preferences of three notoungulates from Santa Cruz (Nesodon imbricatus, Adinotherium ovinum and Protypotherium), typically reconstructed as open habitat grazers. Diets are inferred from enamel microwear features using a low-magnification microscopy technique. Analysis indicates that these notoungulates were primarily feeding on browse, a result that contrasts sharply with previous interpretations based on their hypsodont dentitions. All three notoungulates exhibit a low average number of scratches per taxon, indicative of browsing; high scratch averages are characteristic of grazers. Furthermore, these notoungulates were not primarily feeding on either hard objects (e.g., fruits with seeds) or abrasives (e.g., grasses). Nesodon imbricatus, however, exhibits microwear, suggesting it infrequently fed on hard objects such as bark. The association of tall tooth crowns with browsing diets as demonstrated by the Santa Cruz notoungulates is evidence that hypsodonty does not necessarily indicate open habitat feeding or grazing and that the diets of hypsodont herbivores should be evaluated on a case-by-case basis.