Interphalangeal joints of foot other words, the flexor hallucis longus arises laterally, while the flexor digitorum longus arises medially. The amount of flexion is very considerable, but extension is limited by the plantar and collateral ligaments. Interphalangeal joints of foot The interphalangeal joints of the foot are between the phalanges (bones) of the toes. Since the great toe only has two phalanx bones (proximal and distal phalanges), it only has one interphalangeal joint, which is often abbreviated as the "IP joint." The rest of the toes each have three phalanx bones (proximal, middle, and distal phalanges), so they have two interphalangeal joints: the proximal
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