Aphanosauria calcaneal tuber. Although this structure is smaller in aphanosaurs than in pseudosuchians, it is still much larger than in other avemetatarsalians, most of which don't even possess the structure. A few dinosauriformes also have small calcaneal tubers, although aphanosaurs have larger and rounder tubers than these taxa ("Marasuchus" and a few basal silesaurids). In cross-section, the calcaneal tubers of aphanosaurs are oval-shaped, taller than wide. Most foot material is fragmentary in this group, with only a few phalanges (toe bones) and metatarsals (primary elongated foot bones) known. Based on the length of the preserved metatarsals, the foot was likely rather
Phalanx bone terminal phalanges and fused metacarpal bones able to absorb the stress from running. The sloth spends its life hanging upside-down from branches, and has highly specialized third and fourth digits for the purpose. They have short and squat proximal phalanges with much longer terminal phalanges. They have vestigial second and fifth metacarpals, and their palm extends to the distal interphalangeal joints. The arboreal specialization of these terminal phalanges makes it impossible for the sloth to walk on the ground where the animal has to drag its body with its claws. Phalanx bone The phalanges (singular: "phalanx" ) are digital bones