Xibalbaonyx exinferis n. sp. (Megalonychidae), a new Pleistocene ground sloth from the Yucatán Peninsula, Mexico

ABSTRACT

Recent palaeontological research in submerged caves of the north-eastern Yucatán Peninsula (YP) in Mexico has resulted in the identification of a diverse megafaunal assemblage in the area, among them Late Pleistocene ground sloths assigned to the family Megalonychidae (Xenarthra). Here we report on a new species of Megalonychidae, Xibalbaonyx exinferis n. sp., from a new fossil locality named cenote Tortugas, located west of Puerto Morelos in the federal state of Quintana Roo. The taxon is based on a fragmentary left mandibular ramus, an atlas, and a left humerus. The new taxon is diagnosed by the presence of two mental foramina on the short symphyseal spout, a caniniform being the smallest mandibular tooth, and the anterolaterally directed aperture of the mandibular foramen on the lateral surface of the mandible. Xibalbaonyx exinferis is the third endemic megalonychid documented for the north-eastern Yucatán Peninsula and thus provides increasing evidence for an ecological isolation of the area from the rest of Mexico during the Pleistocene.

KEYWORDS:

• Megalonychidae
• ground sloths
• megafauna
• endemism
• Pleistocene
• Mexico

Acknowledgments

The Tortugas/Cementerio de Xenartros site was first explored by technical and cave diving instructors Vicente Fito and Dirk Penzel. Both discovered the fossil remains documented here. Vicente Fito and his team also participated in the documentation and collection of megafaunal remains from this sinkhole. We would also like to thank Miguel Quintana Pali, Grupo Experiencias Xcaret, Ben Mcgiver, Dive-Xtras, Biol. Karla Peregrina, Biol. Roberto Rojo, Dr. Milagros Varguez and the Red the Planetarios de Quintana Roo. Without their support, sponsorship and dedicated participation in our work, this research would not have been possible.

We are grateful to the careful and thoughtful comments and constructive suggestions by two anonymous reviewers and journal editor Dr. Dyke, which clearly helped to improve the quality of our manuscript.

We gratefully acknowledge financial support by the Federal Ministry of Education and Research (BMBF Projects 01DN119), the German Research Foundation (DFG Project STI 128/28; FR1314/26), and the German Exchange Service (DAAD Kurzreisestipendium für Doktoranden 91683941).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Federal Ministry of Education and Research [Bundesministerium für Bildung und Forschung 01DN119]; German Research Foundation [Deutsche Forschungsgemeinschaft,FR1314/26, STI128/28]; German Exchange Service [Deutscher Akademischer Austauschdienst Kurzreisestipendium für Doktoranden 91683941].