The medial metatarsal depression is large; it is on the medial surface of the proximal end of the tarsometatarsus.
The lateral branch of the tendon on the tarsometatarsus is not ossified (true also of some legs of Tympanuchus).
The greater mass of the bipartite muscle probably makes possible a stronger extension of the tarsometatarsus.
About midway down the tarsometatarsus this tendon becomes ossified.
The tendon continues distally along the tarsometatarsus and the posterior surface of digit IV.
The insertion is tendinous on the posterior surface of the hypotarsus and along the posterolateral ridge of the tarsometatarsus.