The distal tarsalia likewise fuse together, and then on to the upper ends of the metatarsals; the tarsale centrale remains sometimes as a separate osseous nodule, buried in the inter-articular pad.
Of the metatarsals the fifth occurs as an embryonic vestige near the joint; the first is reduced to its distal portion, and is, with the hallux, shoved on to the inner and posterior side of the foot, at least in the majority of birds.
The three middle metatarsals become fused together into a cannon bone; the upper part of the third middle metatarsal projects behind and forms the so-called hypotarsus, which in various ways, characteristic of the different groups of birds (with one or more sulci, grooved or perforated), acts as guiding pulley to the tendons of the flexor muscles of the toes.
The short feet of the penguins are an adaptation.
Third and fourth metacarpals and metatarsals confluent into cannon-bones (fig.
How would you define metatarsals? Add your definition here.