Avian Skeleton

Here's a brief overview of the avian skeleton:

  1. Skull: like other vertebrates, the skull encases the brain, eyes. and ears and posesses two jaw bones, the upper mandible or maxilla and the lower mandible.
  2. Cervical vertebrae: these are the neck vertebrae, numbering between 10 and 26, unlike the 7 found in most mammals. These vertebrae give the bird's neck great flexibility, giving the impression that a bird's neck is broken when one examines a dead bird or one knocked unconscious after flying into glass.
  3. Furcula (medially fused clavicles): this is the "wishbone" and serves to strengthen the shoulder girdle.
  4. Coracoid: this bone opposes the powerful contraction of the major pectoral muscle during the downstroke of the wing. The pectoral or shoulder girdle consists of three bones  to support the wing bones, the coracoid, scapula and furcula = clavicle. The coracoid and scapula form a pocket  for the head of the humerus to attach. The coracoids, scapula and clavicle also form the foramen triosseum, which is a channel for the tendon of an important flight muscle, the supracoracoideus muscle.
  5. Ribs, from 5-10 flattened arches of bone that attach to the last cervical or thoracic vertebrae and the sternum. Uncinate processes project from one rib to an adjacent rib to form a firm ribcage. Thoracic ribs have uncinate processes , which are projections overlapping and fused to adjacent ribs to create a more rigid thoracic cage.
  6. Sternum (with carina): The breastbone is flattened in birds that do not fly, e.g. ostrich. Most birds have a  sternum that resembles the keel of a boat, providing a place for the flight muscles to attach.
  7. Rotula: ball joint of femur
  8. Tarsometatarsus (fused metatarsals, fused with the distal tarsal bones)
  9. Hallux (1st toe)
  10. Tibiofibula (tibia fused with the proximal tarsal bones)
  11. Fibula
  12. Femur
  13. Pubis: the three bones of the pubic girdle provide a place for the head of the femur.
  14. Ischium
  15. Ilium
  16. Caudal vertebrae
  17. Pygostyle (fused posteriormost caudal vertebrae)
  18. Synsacrum (posterior dorsal and sacral vertebrae fused with the ilium)
  19. Scapula - part of the pectoral girdle
  20. Thoracicl vertebrae
  21. Humerus
  22. Ulna
  23. Radius
  24. Carpometacarpus (fused metacarpals, fused with the distal carpal bones)
  25. 3rd finger
  26. 2bd finger
  27. Alula (1st finger)