Dental occlusal surface area in relation to food habits and other biologic features in fossil xenarthrans

VIZCAÍNO, SERGIO FABIÁN; BARGO, MARÍA SUSANA; CASSINI, GUILLERMO HERNÁN

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2006 vol. 43 p. 11 - 26

0002-7014

The Xenarthra includes the most intriguing mammals from the Cenozoic of South America: theglyptodonts (Cingulata) and the ground sloths (Tardigrada). Their masticatory apparatuses are diverseand peculiar, with a strongly reduced, hypselodont dentition that lacks enamel and displays different de-grees of lobation. The goal of this study is to investigate the relationship between dental occlusal surfacearea (OSA) and diet, and other physiological factors in fossil xenarthrans. Over one hundred and fiftyspecimens, including living herbivorous epitherians and both extinct and living xenarthrans, were mea-sured and photographed, and their OSA estimated and plotted against body mass.  For most fossil xe-narthrans OSA is smaller than expected for extant herbivorous mammals of equivalent body size. Withinxenarthrans, cingulates show the highest OSA values, suggesting more extensive oral food processingthan in tardigrades. Among ground sloths, mylodontids have extremely low OSA values, suggesting lowefficiency in oral food processing that was probably compensated by high fermentation in the digestivetract, or lower metabolic requirements, or a combination of both adaptations. On the other hand,Megatherium americanumhas an OSA expected for, or even higher than that of, a mammal of its size, whichindicates higher oral food processing, lower fermentation capacity, and/or higher metabolic require-ments.