Sub-Phylum Vertebrata

Vertebrates may be defined as advance chordate animals those have a cartilaginous or bony endoskeleton consisting of a cranium, housing a brain and a vertebral column through which the nerve cord passes, hence, also called as 'Craniata'. No other group of animals possesses these two fundamental and related characters. Body typically made of head, trunk and a postanal tail. A neck may also be present, especially in the terrestrial forms.

Body covering or integument is a stratified epithelium made of an outer epidermis and an inner dermis; with many mucous glands in aquatic species

Skin covered by a protective exoskeleton comprising scales, feathers, hairs, claws, nails, horns, etc.

Notochord stops short beneath the forebrain, invested by cartilage or bone or replaced by a vertebral column.

A living jointed endoskeleton of bone or cartilage or both, including skull, vertebral column, girdles and limb bones.

Respiration in lower aquatic forms is performed by paired gills; in terrestrial forms by lungs.

Blood vascular system is closed. Heart is ventral, muscular, contractile and consists of 2, 3 or 4 chambers. Blood plasma contains both white and red corpuscles, the latter containing the respiratory pigment, haemoglobin.

Excretion by paired kidneys, mesonephric or metanephric, segmental or non-segmental and discharging through ducts into cloacal or anal region Anterior end of dorsal nerve cord enlarges into a complex brain, protected by skul. Remaining nerve cord forming the spinal

cord surrounded and protected by vertebrae, 10 to 12 pairs of cranial nerves are present in the head An endocrine system of ductless glands scattered through body, regulating body proceses, growth and reproduction Sexes are separate. Gonads paired discharging sex cells through ducts opening into or near the anus There is no asexual reproduction