puboischiofemoralis

Puboischiofemoralis is a skeletal muscle of the pelvic limb found in many reptiles and birds. The name derives from its attachments to the pubis and ischium and its insertion on the proximal femur, reflecting its role across the hip joint. In birds, the muscle is commonly described as consisting of two portions, the puboischiofemoralis externus and puboischiofemoralis internus, though some classifications treat it as a single unit with a shared origin from the puboischial region. The muscle runs from the pelvis to the upper thigh, and its primary function is to move the thigh at the hip, contributing to hip extension, retraction, and stabilization during locomotion. The exact action can vary with species and posture, with different accounts highlighting hip extension, inward rotation, or adduction depending on the limb position. Innervation is typically provided by branches of the femoral nerve.

The puboischiofemoralis forms part of the pelvic limb musculature in sauropsids and shows variations in size and fiber arrangement among taxa. In birds, these muscles interact with other hip and thigh muscles to facilitate leg withdrawal and stepping, while in many reptiles they contribute to the broader system of muscles that control hindlimb movement. Evolutionarily, the puboischiofemoralis is a common component of archosaur and squamate hindlimb anatomy, with avian lineages exhibiting modifications aligned with flight-related and bipedal locomotor specializations.