Bird is a lightweight flying machine

Compared to a lizrd, a bird is a lightweight flying machine of few skeletal parts. Body bones flattened and welded onto a short backbone supporting the wings. The collar bones are fused into a single “wishbone”. The breastbone has a deep keel to provide asurface for attachment of a large flying muscle. The wing is lengthened forelimb. The arm carries the short flight feathers. The wrist and three-fingered hand together support the long primaries. The pelvic bones and lower backbone form a rigid unit.