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ABSTRACT
Associated fragments of a maxilla and mandible of Theosodon hystatus Cabrera and Kraglievich (Macraucheniidae, Litopterna) from the late Miocene Arroyo Chasicó locality (Buenos Aires Province, Argentina) are described and taxonomically reinterpreted. The systematic arrangement is supported by the first phylogenetic analysis of the family. The holotype (MLP 29-IX-1-75) of T. hystatus was originally poorly described and its generic assignation was not fully justified. The comparison of MLP 29-IX-1-75 with Paranauchenia denticulata Ameghino from the ‘Mesopotamiense’ (lower member of the Ituzaingó Formation, Entre Ríos Province; late Miocene) shows significant morphological similarities that lead us to propose that T. hystatus belongs to the genus Paranauchenia Ameghino, resulting in the new combination Paranauchenia hystata. The phylogenetic analysis of Macraucheniidae supports this proposal because both taxa form a monophyletic clade, sharing one synapomorphy: metaconid of m2 lingually placed. This new taxonomic interpretation implies the geographic extension of Paranauchenia to Buenos Aires Province. The obtained phylogeny also corroborates the monophyly of Macraucheniidae, but not that of the currently considered subfamilies, because Cramaucheniinae is paraphyetic.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
ACKNOWLEDGMENTS
We thank the reviewers and the editor for comments that improved the manuscript. We also thank M. Reguero (MLP) and A. Kramarz and S. M. Álvarez (MACN) for facilitating the study of the paleontological collection under their care. J. Noriega and E. Cerdeño improved substantially the manuscript. N. Nuñez Otaño made the drawings. This research was funded by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) of Argentina. PIP-CONICET 886 and 1024; PICT-ANPCYT 392 grants supported this research.
Handling editor: Marcelo Sanchez-Villagra
