The Ruditayoj-Tunasniyoj fossil area (Chuquisaca, Bolivia): a Triassic chirotheriid megatracksite and reinterpretation of purported thyreophoran tracks

ABSTRACT

The South American tetrapod track record is highly diverse and well known mainly from Argentina, Brazil, Bolivia, Chile and Peru. To date, many tracksites are known from Bolivia, most studied during the past century. From the Jurassic-Cretaceous La Puerta Formation of the Tunasniyoj locality (Incapampa-Icla syncline) thyreophoran trackways have previously been described. New geological studies related with the Central Atlantic Magmatic Province in Bolivia recognised the track-bearing unit as the Ipaguazú Formation, dated as Late Triassic in age. In this significantly new context, we present here a new track-bearing locality: Ruditayoj, neighbour to Tunasniyoj, near Icla, Chuquisaca, Bolivia. A detailed study of the trackways from this new site allowed new interpretations consistent with the geological context. Hundreds of Brachychirotherium trackways are present at the site with a wide diversity of preservational types. Behavioural issues such as gregariousness and grouping around ponds are suggested. Trackway parameters, track size and shape support large ‘rauisuchid’ or aetosaur pseudosuchian producers. Previous assignations to thyreophoran producers are discussed. This is the first record of Brachychirotherium from Bolivia, filling the lack of information about suchian fossils, well known in other South American sites.

KEYWORDS:

• Brachychirotherium
• chirotheriidae
• Ipaguazú Formation
• tracks
• Bolivia

Acknowledgments

We want to thank to Ruditayoj community, especially the school teacher Mr Carmelo Cárdenas and Mr Alberto Vargas; to Icla authorities, especially Mayor Mr Gonzalo Salazar Ponce and Tourism Chief Mr Edson García Gutiérrez; to the field support of Adhemar Rodríguez and Grover Marquina; to Lic. Pedro Salazar Collazos, Lic. Beimar Ramallo Sosa, and Lic. Roxana Acosta, authorities of Cultura and Turismo of Sucre City and Chuquisaca Department; to the artist Jorge A. González; and to the photographer and coworker Lucio Mansilla for image and field support. Finally, we are deeply acknowledged to Dr Thierry Sempere who warned us about age mistakes in the geological chart of the area after his participation on the Camiri Sill datation, to Dr Martín Ezcurra, Julia Desojo, and Belén von Baczko for helping in anatomical issues and phylogenetic updating of the involved taxa. We also want to acknowledge to reviewers Heitor Francischini, Spencer Lucas, and Ignacio Díaz Martínez for their careful work which substantially improved the manuscript.

Data deposition

Data of used models and measurements are deposited on page Figshare, DOI: 10.6084/m9.figshare.12685646.

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

The field work was supported by the Universidad CAECE under Grant [res. 418/2017], the Fundación Azara – Universidad Maimónides, and the Fondo Científico In Memorian of Angelines Alonso Benavides.