The last of the oldies: a basal rebbachisaurid (Sauropoda, Diplodocoidea) from the early Late Cretaceous (Cenomanian–Turonian) of Patagonia, Argentina

ABSTRACT

Rebbachisauridae is mainly recorded during the early Late Cretaceous in Gondwana, and in South America in particular. Sidersaura marae gen. et sp. nov. was found in rocks of the Huincul Formation (upper Cenomanian – Turonian) of Neuquén Province, Argentina. Sidersaura has notable characteristics that allow recognising it as a new species and defining its phylogenetic relationships. First, it has a frontoparietal foramen, as in dicraeosauridae. It bears fourteen caudal vertebrae with neural arches displaced closer to the anterior margin of the centrum and a ventral longitudinal hollow on middle of the centra, both characters previously considered as titanosaurian synapomorphies, and here recognised in these diplodocoid sauropods. Sidersaura shows a peculiar tarsal condition with an unusual calcaneum morphology which resembles that of basal sauropods. The haemal arches have a stellate morphology with two sets of projections comparable to the specimen MMCh-PV 47 from the Candeleros Formation (Cenomanian), previously described as a titanosaurian. The phylogenetic analysis retrieves Sidersaura as a basal Rebbachisauridae more closely related to Zapalasaurus than to Limaysaurinae. The presence of a basal taxon at Cenomanian – Turonian times, so close to the extinction of the group, implies that the evolutionary history of rebbachisauridae was more complex than previously thought.

KEYWORDS:

• Neoauropoda
• Rebbachisauridae
• Godwana
• Huincul Formation
• Sidersaura
• Frontoparietal foramen

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2023.2297914.

Acknowledgments

We wish to thank Alejandro Haluza, Rogelio Zapata, Christian Albornoz, Jonatan Aroca, Andrés Moretti, Leonardo Javier Pazo, Mauricio Cerroni, Peter Makovicky, Natan Smith, Akiko Shinya, Johnatan Mitchell, Guillermina Giordano, Federico Gianechini, Ignacio Maniel for the help during the several fieldworks where the remains of Sidersaura were recovered. Special thanks to all the technicians Jonatan Aroca, Rogelio Zapata, Christian Albornoz, Andrés Moretti, Miguel Romero, and Mara Ripoll who prepared all the materials of Sidersaura marae at MMCh. Thanks to the Municipality of Villa El Chocón for all the support in the fieldwork and lab activities. Thanks to the families Zarza and Villoldo Henríquez, owners of Las Campanas field; Luis and Jose Luis Perouene, administrators, for allowing us to enter and work on their property. We would like to thank to Flavio Bellardini and the two anonymous reviewers for their valuable comments and suggestions that greatly improve the article. The first author is grateful for the financial support provided by APA-Bunge y Born for grad students, the Jurassic foundation and The Field Museum. Thanks are also extended to the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Fundación Azara and Municipalidad de Villa El Chocón. This study was also funded by National Geographic (CRE Grant 8826-10; CRE Grant 9300-13) to S.A. and Agencia I+D+i (PICT 2018-04042) to J.I.C.

Disclosure statement

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

Additional information

Funding

The work was supported by the Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación [PICT 2018-04042]; Field Museum [Field Museum Visiting Scholarship]; Jurassic Foundation [Jurassic Foundation]; National Geographic Society [CRE Grant 8826-10; CRE Grant 9300-13]; Asociación Paleontológica Argentina [APA-Bunge y Born].