Features
Vertebrates have bilateral symmetry and are provided with a skull protects the brain, and skeletal cartilage or bone, which comprises a metamerizada axial (spine). The authors know each and almost 62.0001 50.0003 extant species.
The typical vertebrate body are clearly divided into three regions: head, trunk and tail, the trunk is in turn subdivided into thorax and abdomen. Protruding from the trunk limbs, which are odd in pairs in lampreys and other vertebrates. Notochord present in the embryo stage, which is replaced by the spine in the adult, the head is distinct, and shall gather and centralize the majority of sense organs and nervous. The cranial structure of fossilized vertebrates with ease, which has been fundamental for the evolution.
During embryonic development, the walls of the vertebrate body develop holes or gill slits, resulting in the gills (in fish) and different structures. The skeleton can be bone, cartilage, and sometimes present dermoesqueleto, consisting of a skeletal skin formations.

 The vertebrates are classified into five groups:
     mammals
     poultry
     fish
     amphibians
     reptiles