Whales, also called Cetaceans, are a large order of sea-living mammals. They first began evolving in the Paleocene and blossomed in the Eocene. They began as small rat-like animals in the jungles of Pakistan and evolved into the largest mammals on the planet. The primary familes are the Pakicetids, Ambulocetids, Remingtonocetids, Protocetids, Basilosaurids, Durodontids, and the Cetaceans. The Cetaceans of today are divided into two groups: whales are Mysticeti and dolpins and porpoises are Odontoceti. Common members of this order are: Indohyus, Pakicetus, Ambulocetus, Remingtonocetus, Rodhocetus, Kutchicetus, Maiacetus, Protocetus, Basilosaurus, Dorudon, Squalodon, Cetotherium, Kentriodon, Brygmophyseter and Semirostrum.