The tetrapods are the most advanced chordates and are typified by the
presence of lungs, a three- or four-chambered heart, and paired
appendages. Included here are the classes Amphibia (frogs, toads, and
salamanders), Reptilia (lizards, snakes, turtles, and the extinct
dinosaurs), Aves (birds), and Mammalia (including the mammals, such as
men, dogs, whales, etc.).