| rdfs:comment
| - 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 the both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia 53 to 45 mya, resulting in some 30 species adapted to a fully oceanic life; though both echolocation and filter-feeding evolved during a second radiation 36 to 35 mya.
- The Archaeocetes were once thought to have evolved from the mesonychids, based on dental characteristics. However, recent studies in molecular genetics and non-dental morphology show that the first whales or the archaeoceti most likely evolved from artiodactyls; genetic evidence indicates that their closest living relatives are the family Hippopotamidae which includes the modern hippopotamus). The ancestors of archaeocetes probably diverged from the other artiodactyls around the time of the Cretaceous–Tertiary extinction event.
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| abstract
| - 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 the both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia 53 to 45 mya, resulting in some 30 species adapted to a fully oceanic life; though both echolocation and filter-feeding evolved during a second radiation 36 to 35 mya. All archaeocetes from the Ypresian (56–47.8 mya) and most from the Lutetian (47.8–41.3 mya) are known exclusively from Indo-Pakistan, but Bartonian (41.3–38.0 mya) and Priabonian (38.0–33.9 mya) genera are known from across Earth, including North America, Egypt, New Zealand, and Europe. Although there is no consensus regarding the mode of locomotion cetaceans were capable of during the late Lutetian, they were very unlikely to be nearly as well-adapted to the open ocean as living cetaceans. They probably reached as far as America along coastal waters: either around Africa and over to South America, or, more likely, over the Tethys Sea (between Eurasia and Africa) and along the coasts of Europe, Greenland, and North America.
- The Archaeocetes were once thought to have evolved from the mesonychids, based on dental characteristics. However, recent studies in molecular genetics and non-dental morphology show that the first whales or the archaeoceti most likely evolved from artiodactyls; genetic evidence indicates that their closest living relatives are the family Hippopotamidae which includes the modern hippopotamus). The ancestors of archaeocetes probably diverged from the other artiodactyls around the time of the Cretaceous–Tertiary extinction event. Most archeocetes had hind limbs, suggesting that they were fully terrestrial. As the Eocene epoch progressed, the archaeocetes became less terrestrial and more aquatic. Before the Eocene epoch came to an end, one group of archaeocetes, the basilosaurids, gave rise to early modern cetaceans. The Archaeocetes suffered a heavy loss of genera during the Eocene-Oligocene extinction event, but some species survived into the Oligocene. The last archaeocete, which was probably a basilosaurid, became extinct in the Oligocene. They may have become extinct from a combination of competition and climate change.
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