1. Their notochord is replaced by a spinal cord.
2. The anterior part of the hollow nerve forms the brain and the posterior part the spinal cord.
3. They have 5-15 pairs of pharyngeal florets.
4. Lateral pairs of fins or feet act as their locomotion organs.
5. Blood circulatory system is closed type. It is composed of a muscular heart, blood vessels and red blood (containing hemoglobin).
6. Body skin consists of the epidermis (derived from the ectoderm) and the dermis (derived from the mesoderm).
7. 2-4 chambered heart and blood vessels.
8. The brain is protected by the cortex. Brain contains 10-12 pairs of carotid nerves.
9. There is an endoskeleton made of bone or cartilage. Arises from the intraskeletal neural crest.
10. Skin glands, feathers, scales, nails, claws, hairs, horns, hooves etc. exist in the body.
11. There are different types of endocrine glands in the body.
12. Nutrition is complete; Consists of muscular alimentary canal, liver and pancreas.
13. There are well-developed kidneys for excretion and osmoregulation.
[Key words to remember features: spinal cord, brain, mesentery, pharynx, feet, fins, closed circulatory system, carotid nerve, endoskeleton, excretion, osmoregulation]