The inturned head of the femur (the beginnings of the full right-angled femur head seen in dinosaurs and in a different from in mammals); the straight knee joint; the reduced hinge-like ankle joint (technically termed the advanced mesotarsal, or AM, ankle); the long toes and the digitigrade posture of the foot, in which only the toes touch the ground, not the sole of the foot as in earlier archosaurs – and in humans today.
Most of the dinosaur-like characters are also seen in the flying pterosaurs. Certain paleontologists argue that Lagosuchus, the pterosaurs, and the dinosaurs together form a major clade that arose in the Middle to Late Triassic, some 230 million years ago.
The dinosaur-like synapomorphies of this clade, and their further modification in the dinosaurs proper, are part of a major series of related anatomical changes that took place among the archosaurs during the Triassic, and which may have been the key to the origin of the dinosaurs.