First osteological record of a stegosaur (Dinosauria, Ornithischia) from the Upper Jurassic of South America

ABSTRACT

A stegosaurian humerus from the Oxfordian–Tithonian(?) Cañadón Calcáreo Formation of Chubut, Argentina, extends the fossil record of this clade of thyreophoran ornithischian dinosaurs to the Upper Jurassic of South America. The element shares the derived character of an oblique ridge extending from the deltopectoral crest towards the medial distal condyle with taxa such as Kentrosaurus and Stegosaurus and thus represents a derived representative of the clade. The presence of stegosaurs in the Cañadón Calcáreo Formation underlines the similarities of its dinosaur fauna with other Late Jurassic dinosaur faunas, such as the Morrison Formation of North America or the Tendaguru Formation of Tanzania, in at least broad systematic terms.

ACKNOWLEDGMENTS

We thank V. Béland and M. Lex, who found the specimen, and all participants of the November 2019 fieldwork campaign. F. Costa helped with literature and provided photographs of the humeri of the holotype of Miragaia, M. Carrano helped with photos of a humerus of Stegosaurus, J. Kirkland provided photographs of the humerus of Myrmoorapelta, and H. Mallison provided the image of the humerus of Kentrosaurus, all of which is gratefully acknowledged. Critical comments by S. Maidment and an anonymous reviewer helped to improve the manuscript. Fieldwork was made possible by the Secretaría de Cultura of the province of Chubut and by financial support under DFG project RA 1012/26-1 (to OR) and the Fundación Egidio Feruglio.