Overview

The common chicken has the scientific name of Gallus gallus.  It is in the order Galliformes, class Aves, subphylum Vertebrata, and kingdom Animalia. 

The skeletal system of the bird is an excellent example of how evolution has worked toward form and function.  The chicken skeleton can be used to illustrate the various structures and demonstrate how they are well suited for the roles they play, mainly in flight, which birds are known for.

Form and function can be seen in virtually every structure of the skeletal system of the bird.  Studying the skull, reductions and fusions of bones are easy to detect to decrease the weight of birds.  One may also note the large cavity that houses the large brain necessary for coordination for flight. 

Looking at the vertebrae, one may appreciate the number, shape and articulation of vertebrae in comparison to the roles they play.  Because there are many heteroceolus cervical vertebrae allowing for great freedom of movement.  Some vertebrae are fused with ribs to increase strength and decrease weight for flight.  The last few caudal vertebrae are fused to form the pygostyle, which will hold tail feathers that help to increase stability.

Other key features to note when studying are the innominate and synsacrum, which are created by the fusions of either pelvic bones or vertebrae, respectively.  These fusions of the axial system, too, are sturdy and reduce the numbers of muscles necessary for control, thus reducing the overall weight of the bird and facilitating lift.

Most know that some bones, the major limb bones, of birds are hollow and think that the reason is to decrease the weight for flight; however, although some bones are hollow, they have struts to increase the strength of bones and are not significantly lighter than other vertebrate bones of similar size.  Rather, birds have reduced their weights by losing teeth, the large bones needed to support the teeth, most of the tail, and by skull reduction.  The limbs of the appendicular system closely match their functions and have evolve differently than most other vertebrates.  When studying, notice the positions and shapes of the bones of the limbs and learn some of the reasons birds can walk on two feet and soar in the air.