Arches of the foot Arches of the foot The arches of the foot, formed by the tarsal and metatarsal bones, strengthened by ligaments and tendons, allow the foot to support the weight of the body in the erect posture with the least weight. They are categorized as longitudinal and transverse arches. The longitudinal arches of the foot can be divided into medial and lateral arches. The medial arch is higher than the lateral longitudinal arch. It is made up by the calcaneus, the talus, the navicular, the three cuneiforms (medial, intermediate, and lateral), and the first, second, and third metatarsals. Its summit is at
Diandongosuchus The astragalus and calcaneum bones of the ankle fit together like a ball-and-socket, a feature that confirms "Diandongosuchus" as a pseudosuchian. Some of the phalanges or toe bones are missing in ZMNH M8770, but the metatarsals are present and have unique proportions among Triassic archosaurs in which the fourth is longer than the third. A phylogenetic analysis conducted by Li "et al." (2012) in the original description of "Diandongosuchus" showed that it was the most basal member of a clade called Poposauroidea, which includes mostly terrestrial pseudosuchians such as the bipedal "Poposaurus" and the sail-backed "Arizonasaurus". It was found to