Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (55 to 23 million years ago). Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution and are thus the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti.