Femur the medial, gives attachment to the fibular collateral ligament of the knee-joint. The femur develops from the limb buds as a result of interactions between the ectoderm and the underlying mesoderm, formation occurs roughly around the fourth week of development. By the sixth week of development, the first hyaline cartilage model of the femur is formed by chondrocytes. Endochondral ossification begins by the end of the embryonic period and primary ossification centers are present in all long bones of the limbs, including the femur, by the 12th week of development. The hindlimb development lags behind forelimb development by 1–2 days.
Vancleavea of archosaurs as well as the internal trochanter of basal archosauriforms. The midshaft of the femur is circular in cross-section. The lower portion of the femur includes both a medial condyle (which connects to the tibia) and a lateral condyle (which connects to the fibula), although neither of these knobs are particularly strongly developed. In general, the femur of Vancleavea is intermediate in structure between basal archosauriforms and archosaurs. The tibia and fibula (lower leg bones) are both slightly curved away from the center of the leg. They are also thinnest at their respective midshafts. The front edge of the