Stagonolepis robertsoni (Agassiz 1844) Late Triassic ~210 mya ~3 m in length, was derived from a sister to Aetosaurus.
Distinct from Aetosaurus, Stagonolepis had a smaller skull and a deeper torso. The skull shape was virtually identical. The pelvis was larger. The hands had shorter metacarpals. The feet had shorter metatarsals. The longes claws were the medial ones. The calcaneal heel turned up posteriorly.