Tetrapoda
From Conservapedia
The superclass Tetrapoda (from the Greek tetrapodē, meaning "four footed") refers to all vertebrates that possess four limbs. This includes amphibians, reptiles, birds and mammals. In fact, all land-based vertebrates are tetrapods.
Some tetrapods, like whales and snakes, possess vestigial remains of limbs and are thus included in the superclass.