I. According to mode of formation:
These bones develop from the pre-existing cartilage. These are also called as endochondrial bones. E.g. humerus, femur.
These bones develop in the dermis of the skin as thin plates and sink to get attached over original cartilages. E.g. frontal nasals, vomers, parietals of the skull.
These are small rounded masses of bones formed in tendons at the joints where they are subjected to great pressure. E.g. patella (knee cap), fabellae
These bones are formed in organs dissociated from the rest of the skeleton. In the heart of some ungulates (ruminates) bones develops in the connective tissue of the cardia C (skeleton) as Os cordis.
Bony matter occurs as bars, whose spaces are filled with red bone marrow. They occur at the end of long bones. E.g. femur, humerus, flatbones, sternum etc.
Compact matrix occurs in the form of lamellae. E.g. clavicles and scapulae of pectoral girdles, armbones, limbbones and innominates of pelvic girdle.
II. According to shape and size:
1. Long bones: Humerus, radius, ulna, femur, tibia, fibula
2. Short bones: Carpals and tarsals
3. Flat bones: Skull bones, sternum and ribs
4. Irregular bones: Ear ossicles, vertebrae, carpals of wrists and tarsal of ankle.