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). 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.
Temporal range: 50–23 Ma
|Cynthiacetus and Ambulocetus skeletons|
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 .
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.
The group is a paraphyletic because it gave rise to the two separate modern suborders.
- "Archaeoceti". Paleobiology Database. Retrieved 20 September 2018.
- Thewissen J.G M. & Williams E.M. 2002. The early radiations of Cetacea (Mammalia): evolutionary pattern and developmental correlations. Annual Review of Ecology and Systematics 33 (1): 73–90.  Archived 2021-02-24 at the Wayback Machine
- Fordyce, Ewan 2002. Cetacean evolution. In Perrin, William R. et al Encyclopedia of marine mammals. Academic Press. pp. 214–25. ISBN 0-12-551340-2
- Geisler, J.H; Sanders A.E. & Luo, Zhe-Xi 2005. A new protocetid whale (Cetacea, Archaeoceti) from the late middle Eocene of South Carolina. American Museum Novitates 3480: 1–68.  Archived 2015-02-26 at the Wayback Machine