Saurodesmus robertsoni – the oldest Scottish cynodont

184 years ago, a small bone was discovered in the Triassic of Scotland. Even though over the decades it was examined by some of the most significant paleontologists of their time, named Saurodesmus robertsoni, and variably interpreted as a femur of a turtle, humerus of a crocodile, or a bone of an animal resembling pareiasaurs or cynognathians, its systematic identity was never really established. To finally solve this mystery, the anatomy of amniote stylopodial bones is reviewed. The specimen is reassessed as a femur of a derived (probably tritylodontid) cynodont.

Figure: the studied specimen – photograph (left) and 3D model (middle) – and a phylogenetic tree of amniotes considered in the paper indicating the probable position of Saurodesmus robertsoni (right).