archaeopteryx
is the most ancient, primitive bird. He lived around 150 years ago in what is now Southern Germany. His features make him look like something between a dinosaur and a bird
Arthuritis
or arthritis, as it is also known, is an illness which causes stiffness, pain and fatigue, as well as swelling and inflammation of the joints. This desease can affect not only the joints but other parts of the body such as muscles, bones, tendons and other internal organs.
calcification
process by which calcium salts cause the soft tissue of the bone to harden
ossification
formation of normal, healthy bone tissue
pneumatisation
presence or development of air-filled cavities in the bone