A distal femur end of a Stegosauria dinosaur from the Upper Jurassic (Tithonian) of the Cameros Basin (Aguilar del Río Alhama, La Rioja province, Spain)

Abstract

This paper describes the distal end of the femur of a dinosaur from the Upper Jurassic of Aguilar del Río Alhama (La Rioja), in the eastern part of the Cameros Basin. Discovered in 2001, it has unfortunately been delocalized for many years, so that it has not been possible to provide an adequate description and interpretation of it before. Although the material is very fragmentary, the morphology of both condyles (tibial and fibular) is well observed. The shallow intercondylar groove, the clearly bilobulated and very wide morphology in distal view, as well as the morphometric indices analyzed, indicate that this specimen could belong to a stegosaurid dinosaur, probably close to the genera Stegosaurus and Dacentrurus. The area of the tibial condyle (mostly on its anterior face) presents a fracture of tectonic origin that is filled with quartz and calcite crystals. This finding constitutes the first osteological remain of the Stegosauria clade in the eastern sector of the Cameros Basin which, together with some ichnites of thyreophorans already known in this area, represents a significant complement on the presence of stegosaurian dinosaurs in the vertebrate communities of the last phase of the Jurassic in the Cameros Basin.