Evaluating habitats and feeding habits through ecomorphological features in glyptodonts (Mammalia, Xenarthra)

VIZCAÍNO, S. F.; CASSINI, G. H.; FERNICOLA, J. C.; BARGO, M. S.

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

Glyptodonts are very peculiar extinct mammals of the New World that vanished as part of the great end-Pleistocene extinction of continental mammals. The goal of this study is to evaluate ecomorphological variables in glyptodonts from different ages (Miocene to Pleistocene), clades, and sizes, with the purpose of inferring their habitats and feeding habits. The analyses include estimation of body masses and three variables: dental occlusal surface area (OSA), relative muzzle width (RMW) and hypsodonty index (HI). The major deviations from the correlation between OSA and body mass are recorded in two of three taxa larger than 1000 kg: Panochthus Burmeister, 1866 and Doedicurus Burmeister, 1874. The first lies markedly above the regression line and the latter well below, suggesting that these two forms resulted from divergent evolutionary pathways. RMW allows the distinction of two main groups: the small-sized Early Miocene propalaehoplophorids were selective feeders, while the larger post-Miocene forms were more bulk feeders. The Pleistocene Glyptodon Owen, 1839 appears as an exception, implying a reversion to a selective feeding behavior. The relation between RMW and HI allows discriminating feeding niche partitioning in glyptodonts. Among the early Miocene propalaehoplophorids, Eucinepeltus Ameghino, 1891 would have been a highly selective feeder in relatively closed environments, Propalaehoplophorus Ameghino, 1887 a highly selective feeder in moderately open habitats, and Cochlops Ameghino, 1889 a less selective feeder in moderately open habitats. Among the large Pliocene and Pleistocene taxa, Neuryurus Ameghino, 1889 and Neosclerocalyptus Paula Couto, 1957 were probably bulk feeders in relatively open environments, while Panochthus and Doedicurus were bulk feeders in open environments. Alternative interpretations can be assessed for Glyptodon: it was a more selective feeder in closer habitats, or had a different feeding behavior, browsing on specific plants at higher levels from the ground, and/or a specialized physiology. The late Miocene and Pliocene forms (Hoplophractus Cabrera, 1939, Eosclerocalyptus Ameghino, 1919, and Urotherium Castellanos, 1926) were probably intermediate between the Miocene and the Pleistocene ones.