A new South American archaic ungulate and new insight for the early diversification of the South American native ungulates

ABSTRACT

Palaeogene South American faunas include enigmatic ungulates that cannot be classified unequivocally within any of the main South American (SA) Native Ungulates clades (Litopterna, Notoungulata, Astrapotheria, Pyrotheria and Xenungulata) because they retain plesiomorphic features, resembling Laurasian ‘archaic ungulates’ traditionally classified within the order ‘Condylarthra’. Most SA ‘condylarths’ are known by partial dental series and isolated teeth and unassociated postcranial remains, hampering comparisons with better-known ungulates. Here, we describe a nearly complete skull and associated mandible of an SA ‘condylarth’, Talquinodus puertai gen. et sp. nov., preserving most of the dentition and basicranium, derived from middle Eocene rocks of the Sarmiento Formation at Central Patagonia. Talquinodus shows a combination of plesiomorphic traits (complete dentition with bunolophodont cheek teeth, ring like ectotympanic, retention of stapedial system, etc.), combined with some autapomorphies, as the reduction of the m3 talonid. Our phylogenetic analyses support consistently that Talquinodus belongs to the SA radiation of Euungulata along with Litopterna, Notoungulata and Astrapotheria. However, the internal relationships could not be resolved unambiguously: Talquinodus could be a didolodontid related to the origin of Litopterna, or could be part of a separate radiation of South American archaic ungulates, along Depaulacoutoia, Lamegoia and Escribania, with no descendants in post-Eocene faunas.

KEYWORDS:

• South America
• “condylarthra”
• Eocene
• skull
• ear anatomy
• phylogeny

Acknowledgments

We thank to J. Genise, M.V. Sánchez, L. Cantil (MACN), M. Verde (Universidad de la República de Uruguay), and the MPEF technical staff for assistance during fieldtrips at Sierra Talquino. We also thank Mrs Ritter, who has granted us access to her property. We are especially indebted to G. Aguirrezabala for the preparation of the studied specimen. Francisco De Cianni also helped with the mechanical preparation. L. Bergqvist (Universidade Federal do Rio de Janeiro, Brazil) provided valuable photos of Depaulacoutoia protocenica. To O. Maridet (JURASSICA Museum) for his help with softwares. To J. González for the drawings of Figure 10. To G. Martinez and an anonymous reviewer for their pertinent corrections and thoughtful suggestions, which greatly improved the quality of this paper. Financial support by PIP CONICET 0058 and PICT FONCyT 2017-1265 to E.B.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data generated and analysed during this study are included in the present published article and associated supplementary files.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2024.2380810.

Additional information

Funding

This work was supported by the Consejo Nacional de Investigaciones Científicas y Técnicas under Grant PIP CONICET 0058 and Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación under Grant PICT FONCyT 2017-1265 to Eduardo Bellosi and PICT-2030-SerieA-03832 to Marcelo Krause.