Tetrapod

Tetrapoda Temporal range: Middle Devonian to Recent
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Teleostomi
Superclass:	Tetrapoda Broili, 1913
Subgroups
Batrachomorpha (Amphibia, temnospondyli, and lepospondyli) Reptiliomorpha

Tetrapods (Greek tetrapoda = four feet) are vertebrate four-legged land animals. This kind of locomotion is called quadrupedal.

Amphibians, reptiles, dinosaurs (including their direct descendants, the birds), and mammals are all tetrapods. Even though snakes do not have limbs, they are tetrapods because they evolved from animals with four limbs.

The earliest tetrapods evolved from the Sarcopterygii (lobe-finned fish) into air-breathing amphibians, perhaps in the Upper Devonian period.^[1] This means the transition took place in fish, before the land was the main habitat. This is typical of transitional fossils undergoing mosaic evolution.

1. ↑ Clack, Jennifer 2012. Gaining ground: the origin and early evolution of tetrapods. 2nd ed, Bloominton, Indiana: Indiana Umiversity Press, 127, 143 et seq. ISBN 978-0-253-35675-8, (Tetrapod at Google Books)