The ankle of "Westlothiana" was similar (but probably not identical) to that of basal amniotes, rather than amphibians. In modern amphibians and most non-amniote tetrapods, the ankle is formed by twelve bones. Five small, rounded ankle bones, known as "distal tarsals", connect to the metatarsal bones which each lead to a toe. Three somewhat larger ankle bones, known as "proximal tarsals", connect to the bones of the lower leg. These three are the medium-sized (which connects to the fibula), the small (which connects to the tibia), and the quite large which lies in the middle and contacts both the fibula and tibia. Four small numbered bones known as "" fill in the gaps between the proximal and distal tarsals.