Sanjuansaurus was comparable in size to a medium-sized Herrerasaurus, with a thigh bone that was 395 millimetres (15.6 in) long and a tibia that is 260 millimetres (10 in) in length. Alcober and Martinez performed a phylogenetic analysis and found Sanjuansaurus to be a herrerasaurid.[1] It was determined that Sanjuansaurus and Herrerasaurus share many similarities in the morphology of the skull, neck vertebrae, back vertebrae, hip vertebrae, scapula, and the hip bones. Alcober and Martinez observed that Sanjuansaurus and Staurikosaurus share many similarities in the morphology of the hip bones, and the tibia.The pubis of Sanjuansaurus, unlike in other herrerasaurids, points toward the cranium.