5 Vertebrate Groups
Fishes: The first fishes are thought to have emerged some 518 million years ago during the Cambrian Period of Earth’s history.
Amphibians: Amphibians evolved from fully aquatic tetrapods who descended from lobe-finned fish—sometime.
Reptiles: Reptiles are air-breathing vertebrates.
Birds: Birds make up any of the 9,600 living species unique in having feathers, the major characteristic that distinguishes them from all other animals.
Mammals: There are approximately 5,000 species of mammals living today.