part of develops from ends during starts during death hindlimb skeleton femur xenopus_anatomy UBERON:0000981 Either of the paired, elongate, cylindrical bones of endochondral origin that form the thighs, extending from the pelvic girdles to the knees. Proximal bone of the hind leg, which begins to ossify at NF stage 55. XAO:0003214 endochondral bone femur rudiment hindlimb stylopod NF stage 55