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Archaeoceti Fossil range: Eocene to Miocene (non-Autocetan)
Pakicetus, one of the very first archeocetids
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Cetacea Suborder: Archaeoceti
Families and Clades
see text

Archaeocetids, or "ancient whales", are a paraphyletic group of cetaceans that gave rise to Autoceti - the new cetaceans. The archaeoceti 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 (perhaps of the family Hippopotamidae which includes the modern Hippopotamus). The ancestors of archaeoceti probably diverged from artiodactyls in the Latest Cretaceous or Early Paleocene. Most archeocetids had hind limbs unlike the cetaceans of today. The very first archaeocetid was probably fully terrestrial. As the Eocene progressed the archaeocetids were becoming less terrestrial and more aquatic. By the Late or latest Eocene the archaeocetids, the basilosaurids gave rise to early modern cetaceans. The Archaeoceti managed to survive the Eocene-Oligocene extinction event, but they suffered a heavy loss of genera. The Archaeoceti were common early in the Oligocene, but not as common as in Eocene. The last archaeoceti became extinct in the Miocene, which was probably a basilosaurid, probably because of competition with the toothed cetaceans and the new sharks appearing in the Miocene (e.g. Megalodon). Another explanation is climate change; as Miocene progressed, the ocean became cooler and cooler. They may have became extinct in the combination of the two factors.

Contents 1 Taxonomy and Phylogeny 1.1 Phylogeny 2 See also 3 External links

• Superorder Cetartiodactyla (or Acreodi)
  • Order Cetacea
    • Suborder Archaeoceti
      • • Genus ?Ferecetotherium (the most primitive cetacean)
        • Family Pakicetidae
      • (?unranked) ?Ambulocetoidea
        • • Genus Himalayacetus
          • Genus Gandakasia
        • Family Ambulocetidae
          • Genus Ambulocetus
        • Family Remingtonocetidae
        • Family Protocetidae
        • Subfamily Indocetinae
          • Genus Protocetus
          • Genus Georgiacetus
        • Family Basilosauridae
          • Subfamily Basilosaurinae
            • Genus Basilosaurus
          • Subfamily Dorudontinae
            • Genus Dorudon
    • (unranked) Autoceta
    • Suborder Mysticeti
    • Suborder Odontoceti
      • (unranked) Squalodontoidea
        • Genus Squalodon

Cetartiodactyla
|--Cetacea
|  |--Pakicetidae 
|  `--+--Ambulocetidae 
|     `--+--Remingtonocetidae 
|        `--Protocetidae
|           |--Georgiacetus
|           `--Basilosauridae
|              |--Basilosaurus
|              `--+--Dorudon 
|                 `--Autoceta
|                    |--Odontoceti 
|                    |  |--Squalodontoidea 
|                    |  |  |--Squalodontidae 
|                    |  |  `--Rhabdosteidae
|                    |  `--Physeteroidea 
|                    `--Mysticeti 
`--Artiodactyla

• Evolution of cetaceans
• Cetaceans
• Mesonychid
• Cetartiodactyla

• Archaeoceti