Haversian system is a diagnostic feature of-
a. Avian bones
b. Reptilian bones
c. Mammalian bones
d. Bone of all animals

Hint: A network of tubes, created by lamellas, around narrow channels. In the bone matrix of long bones, such as humerus, these canals connect blood vessels and nerve fibres throughout the bone and interact with osteocytes.

Complete answer:
> Option A is incorrect. The skull, humerus, clavicle, keel, pelvic girdle, and the lumbar and sacral vertebrae comprise pneumatic bones. Medullary bones are another significant bone of the avian skeleton. These bones are composed of the tibia, femur, pubic bone, ribs, ulna, toe bones, and the scapula.

> Option B is incorrect. The bone, articular bone, and columella of the reptilian quadrate formed into the mammalian incus, malleus, and stapes (anvil, hammer, and stirrup), respectively. Among reptiles, the eardrum is connected to the inner ear by a single bone, the columella, while the upper and lower jaws contain several bones not found in mammals.

> Option C is correct. The structural unit of a compact bone is known as the Haversian system or osteon. Each Haversian system is an extended cylinder parallel to the longitudinal plane of the bone that is oriented. It consists of a central Haversian canal running longitudinally with concentric rings (lamellae) of bone matrix. Nerves and blood vessels are transported to all parts of the bone through the Haversian canal. A diagnostic feature of mammalian bones is the Haversian system.

> Option D is incorrect. There are many special characteristics of the skeletal system of mammals. The lower mammalian jaw is made of just one bone, the dental jaw. Some vertebrates' jaws are made up of more than one bone.

Hence, the correct answer is option (C).

Note: The Haversian system gives bone protection and strength. Compact bone tissue is made up of units called Haversian systems or osteons. Osteons are cylindrical structures containing a mineral matrix and living osteocytes linked by blood-carrying canaliculi and are directed parallel to the bone's long axis.