Archaeoceti
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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

Archaeocetes, or "ancient whales", are a paraphyletic group of cetaceans that gave rise to the modern cetaceans. 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 (perhaps of the family Hippopotamidae which includes the modern Hippopotamus). The ancestors of archaeocetes probably diverged from the artiodactyls around the time of the Cretaceous–Tertiary extinction event. Most archeocetes had hind limbs, suggesting that they were likely fully terrestrial. As the Eocene epoch progressed the archaeocetes were becoming 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 archaeocetes became extinct in the Oligocene, which was probably a basilosaurid. Another explanation is climate change; as Miocene progressed, the ocean became cooler and cooler. They may have become extinct in the combination of the two factors: competition and climate change.

The remingtonocetids

The more aquatic Basilosaurus.

Taxonomy and Phylogeny

• Superorder Cetartiodactyla
  • Order Cetacea
    • Suborder Archaeoceti
      • • Family Pakicetidae
          • Genus Pakicetus
          • Genus Nalacetus
          • Genus Ichthyolestes
        • Family Ambulocetidae
          • Genus Ambulocetus
          • Genus Gandakasia
          • Genus Himalayacetus
        • Family Remingtonocetidae
          • Genus Andrewsiphius
          • Genus Attockicetus
          • Genus Dalanistes
          • Genus Kutchicetus
          • Genus Remingtonocetus
        • Family Protocetidae
          • Genus Rodhocetus
        • Subfamily Indocetinae
          • Genus Protocetus
          • Genus Georgiacetus
        • Family Basilosauridae
          • Subfamily Basilosaurinae
            • Genus Basilosaurus
          • Subfamily Dorudontinae
            • Genus Zygorhiza
            • Genus Dorudon
    • Suborder Mysticeti
    • Suborder Odontoceti
      • (unranked) Squalodontoidea
        • Genus Squalodon

Phylogeny

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

See also

Cetaceans portal

Paleontology portal

• Evolution of cetaceans
• Cetaceans
• Mesonychid
• Cetartiodactyla

References

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (June 2008)

External links

• Archaeoceti
• Archaeoceti and Basilosaurus