Fourth trochanter

The fourth trochanter is a shared characteristic common to archosaurs. It is a knob-like feature on the posterior-medial side of the middle of the femur shaft that serves as a muscle attachment, mainly for the Musculus caudofemoralis longus, the main retractor tail muscle that pulls the thighbone to the rear. The fourth trochanter first appeared in the Erythrosuchidae, large basal archosauriform predators of the early Triassic period.

Fourth trochanter

The fourth trochanter is a shared characteristic common to archosaurs. It is a knob-like feature on the posterior-medial side of the middle of the femur shaft that serves as a muscle attachment, mainly for the Musculus caudofemoralis longus, the main retractor tail muscle that pulls the thighbone to the rear. The fourth trochanter first appeared in the Erythrosuchidae, large basal archosauriform predators of the early Triassic period.