Tarsometatarsus

The tarsometatarsus is a bone that is only found in the lower leg of birds and certain non-avian dinosaurs.

It is formed from the fusion of several bones found in other types of animals, and homologous to the mammalian tarsal (ankle) and metatarsal (foot) bones. Despite this, the tarsometatarsus of birds is often referred to as just the tarsus or metatarsus.