Abstract
All xenarthrans known to date are characterized by having permanent teeth that are both high crowned and open rooted, i.e., euhypsodont, and with a type of hypsodonty different from that of the rest of Placentalia: dentine hypsodonty. Also, most xenarthrans lack enamel; however, its presence has been reported in the fossil armadillo Utaetus buccatus and in living Dasypus. Considering the divergence of Xenarthra from other eutherians that possessed enameled teeth, the absence of enamel is a derived character. Diverse specializations are known in the dentition of xenarthrans, but the primitive pattern of their teeth and dentitions is still unknown. Here, we describe the mandible and teeth of a fossil armadillo, Astegotherium dichotomus (Astegotheriini, Dasypodidae), from the early Middle Eocene of Argentine Patagonia, with teeth showing both true enamel and closed roots. It is the oldest xenarthran with mandibular remains exhibiting protohypsodonty and is therefore likely representative of ancestral cingulates and xenarthrans generally. Astegotherium supports a recent hypothesis based on molecular data that enamel loss occurred independently not only within xenarthrans but also within dasypodid armadillos.
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Abbreviations
- MMP:
-
Museo Municipal de Ciencias Naturales de Mar del Plata “Lorenzo Scaglia” Mar del Plata, Argentina
- MPEF:
-
Museo Paleontológico Egidio Feruglio Trelew, Argentina
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Acknowledgments
Many thanks to Alejandro Dondas (MMP, Mar del Plata, Buenos Aires) for providing access to and loan of the valuable material for this study; E. Ruigómez for access to specimens at MPEF (Chubut); Richard Madden for interesting discussions on hypsodonty; Robert Asher, Darin Croft, and two anonymous reviewers for valuable suggestions that improved the original manuscript; Diego Brandoni for logistical support; and Cecilia Morgan for help with the English text. We acknowledge financial support from Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET) and Universidad Nacional de La Plata (UNLP, FCNYM N-593 to A.A.C).
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Communicated by: Robert J. Asher
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Ciancio, M.R., Vieytes, E.C. & Carlini, A.A. When xenarthrans had enamel: insights on the evolution of their hypsodonty and paleontological support for independent evolution in armadillos. Naturwissenschaften 101, 715–725 (2014). https://doi.org/10.1007/s00114-014-1208-9
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DOI: https://doi.org/10.1007/s00114-014-1208-9