Postcranial morphology of Notopithecus Ameghino, 1897 (Notoungulata, Interatheriidae) from the middle Eocene of Patagonia, Argentina

ABSTRACT

The genus Notopithecus is the best known and most abundant among the genera traditionally grouped as “Notopithecinae” (Notoungulata, Interatheriidae). Previous studies have described in detail the morphology of the skull of Notopithecus; however, its scarce appendicular bones were poorly characterized. Until now neither skulls nor associated skeletons were known for the other genera of this group. In this paper, the most complete individual of Notopithecus is described. The specimen MPEF-PV 1113 is in the vertebrate paleontology collection at the Museo Paleontológico Egidio Feruglio, Trelew, and comes from Valle Hermoso, Chubut Province, Argentina. It includes the articulated cranium and mandible and most of the postcranial skeleton, with almost all the elements in anatomical position: many articulated vertebrae, scapula, humerus, radius, femur, tibia, fibula, calcaneum, astragalus, metapodials, and phalanges. The present contribution constitutes the first comparative study of the postcranial skeleton associated with the skull of an individual of Notopithecus, clarifying some systematic contradiction relative to the holotype of this taxon; at the same time, most of these elements are known for the first time for notopithecines. The appendicular skeleton of Notopithecus is significantly distinct from other known interatheriine interatheriids such as Federicoanaya sallaensis and Eopachyrucos ranchoverdensis from the Deseadan SALMA or Interatherium and Protypotherium from the Santacrucian SALMA. On the other hand, it presents some similarities with the Mesotheriidae Trachytherus and the generalized notoungulate Colbertia magellanica. The new specimen of Notopithecus offers the potential for morphofunctional studies and improving our understanding of the phylogeny of this group.

ACKNOWLEDGMENTS

I thank the reviewers and the editor of the Journal for the constructive suggestions and improvement of the manuscript; E. Cerdeño (IANIGLA) for her critical reading and valuable comments; N. Horak for assisting with the English version; E. Ruigómez and D. Pol (MPEF) for facilitating the specimen object of this study; and B. MacFadden and R. Hulbert (UF), A. Kramarz (MACN), and M. Reguero (MLP) for permitting the study of the paleontological collections under their care. Special thanks to O. Sanisidro for creating the reconstruction of Notopithecus, A. Elissamburu for her suggestions on the reconstruction, and R. Marin (MAGRAF) for helping with the figures. This research was financially supported by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), a Fundación Williams grant, and an International Student Travel Grant, Vertebrate Paleontology, from University of Florida.

Handling editor: Guillermo Rougier