A new small-bodied ankylosaurian dinosaur from the Upper Cretaceous of North Patagonia (Río Negro Province, Argentina)

Abstract

The most representative ankylosaurian remains from Argentina have been found in sediments of the Allen Formation (Campanian–Maastrichtian) in Salitral Moreno, Río Negro Province. Several authors have discussed the identity and history of these remains. In this study, we review all published material along with some new remains in order to summarize all the knowledge about these ankylosaurs. Previously published material includes a tooth, dorsal and anterior caudal vertebrae, a femur and several osteoderms. The new remains include synsacral and caudal elements, a partial femur and osteoderms. The anatomy of the tooth, the synsacrum, the mid-caudal vertebra, the femur and the osteoderms, and the histology of the post-cervical osteoderms, support a nodosaurid identification, as proposed in previous descriptions of the Salitral Moreno material. Patagopelta cristata gen. et sp. nov. is a new nodosaurid ankylosaur characterized by the presence of unique cervical half-ring and femoral anatomies, including high-crested lateral osteoderms in the half rings and a strongly developed muscular crest in the anterior surface of the femur. The ∼2 m body length estimated for Patagopelta is very small for an ankylosaur, comparable with the dwarf nodosaurid Struthiosaurus. We recovered Patagopelta within Nodosaurinae, related to nodosaurids from the ‘mid’-Cretaceous of North America, contrasting the previous topologies that related this material with Panoplosaurini (Late Cretaceous North American nodosaurids). These results support a palaeobiogeographical context in which the nodosaurids from Salitral Moreno, Argentina, are part of the allochthonous fauna that migrated into South America during the late Campanian as part of the First American Biotic Interchange.

https://zoobank.org/urn:lsid:zoobank.org:pub:FBA24443-F365-49FD-A959-10D2848C2400

Keywords:

• Patagopelta
• Nodosauridae
• Late Cretaceous
• Salitral Moreno
• Patagonia
• Gondwana

Acknowledgements

We thank the Secretaría de Cultura of the Río Negro Province, I. Cerda, R. Juárez Valieri and the staff of the Museo Provincial ‘Carlos Ameghino’ for allowing us to study the material; and we thank the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación (project PICT 2018-04598), and the Fundación Azara-Universidad Maimónides for the funding. The research of XPS is supported by the Basque Government (group IT1418-19 and IT1485-22), the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (project CGL2017-85038-P and PID2021-122612OB-I00). FJR thanks A. Murray, F. Garberoglio, J. M. Albite, M. Hoqui and L. Pazo for assistance; L. Leahey, K. Carpenter, the Museum für Naturkunde (Berlin), the Smithsonian National Museum of Natural History (Washington, DC; si.edu/collections) and the Yale Peabody Museum of Natural History (New Haven, collections.peabody.yale.edu) for digital material; L. Pazo for specimen preparation and type container packaging; and to I. Cerda for histological advice. Many thanks to the reviewers Susannah Maidment and Attila Ősi, whose comments strongly improved the manuscript.

Supplemental material

Supplemental material for this article can be accessed here: https://doi.org/10.1080/14772019.2022.2137441.

Associate Editor: Richard Butler