Cetaceans are a diverse infraorder of marine artiodactyls (even toed ungulates). They first appeared in the Paleocene (though the earliest identifiable specimens were found in the Eocene). The earliest whales resembled small mammals like raccoons and deer, living in the jungles of Pakistan, and ventured into the water, either to avoid predators, find food due to a lack of food on land, or both. It was during this period that they eventually evolved into the mammals we see today, giving rise to the various whale and dolphins that have existed. One example being the blue whale, the largest extant animal on the planet. The primary groups are the Archeocetes (Pakicetids, Ambulocetids, Remingtonocetids, Protocetids, Basilosaurids, Durodontids) and the Neocetes (Odontoceti, Mysticeti).