Archaeoceti

Archaeoceti Temporal range: 50–23 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Cynthiacetus and Ambulocetus skeletons
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Infraorder:	Cetacea
Parvorder:	†Archaeoceti Flower, 1883

The Archaeoceti ('ancient whales'), or Zeuglodontes in older literature, is a group of primitive cetaceans. They lived from the early Eocene to the late Oligocene, 55–23 million years ago (mya).^[1] They were the first cetacean radiation, and they include the first amphibious stages in cetacean evolution. So they are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti.^[2]

The group evolved in the shallow waters that separated India and Asia 55–45 mya. About 30 species have been found which were adapted to a fully oceanic life. Modern characters such as echolocation and filter-feeding evolved later, in a second radiation 36 to 35 mya.^[3]

All archaeocetes from 55 to 48 mya are only from Indo-Pakistan. By 41–34 mya genera are known from across the Earth, including North America, Egypt, New Zealand, and Europe. They were very unlikely to be as well-adapted to the open ocean as living cetaceans, so they probably got to North America along coastal waters. They could have gone around Africa and over to South America. More likely, over the Tethys Sea (between Eurasia and Africa) and along the coasts of Europe, Greenland, and North America.^[4]

The group is a paraphyletic because it gave rise to the two separate modern suborders.