Cetartiodactyla

The cetartiodactyls (Cetartiodactyla) are an order of placental mammals that brings together the ancient orders of cetaceans (Cetacea) and traditional artiodactyls (Artiodactyla). Cetaceans are dolphins, whales and the like. Artiodactyls are characterized by having cloven hooves, such as camels, cows, goats, sheep, deer, giraffes, pigs, hippos, etc. Some classifications use the term Artiodactyla for this order, but others prefer Cetartiodactyla, however both terms are synonymous since cetaceans should be included in the artiodactyls according to cladistics.

The oldest fossils of this group date from the Eocene, however phylogenetic analyzes place their origin at the end of the Cretaceous.

Phylogeny

For a long time, the dominant hypothesis about the origin of cetaceans placed it in the mesonychia (Mesonychia), an extinct order of carnivorous ungulates closely related to artiodactyls.

Recent fossils found in Pakistan and assigned to the genera Pakicetus and Ambulocetus, have come to confirm that cetaceans evolved from artiodactyls, when these had already differentiated of their mesonychian ancestors. The first clues about this relationship arose around 1990, by comparing molecules and genes between current mammals. Evidence for a specific relationship to hippopotamuses, which are artiodactyls, is conclusive. In any case, hippos offer an approximate image of what the first forms of cetaceans must have been like. The following cladogram shows these putative relationships:

Classification

The order contains the following groups, listed here with the rank they have classically received:

• Order Cetartiodactyla
  • Suborden Tylopoda
    • † Anoplotheriidae
    • † FamilyChoeropotamidae
    • † FamilyCainotheriidae
    • † FamilyMerycoidodontidae
    • † FamiliaAgriochoeridae
    • Family Camelidae:
    • † FamilyOromerycidae
    • † FamiliaXiphodontidae
  • Suborden Suina
    • Suidae Family:
    • Tayassuidae Family:
    • † FamilySanitheriidae
  • Suborden Cetancodonta
    • • GenderAndrewsarchus
      • † FamilyEntelodontidae
      • † FamiliaRaoellidae
      • † FamiliaDichobunidae
      • † Helohyidae
      • † FamilyCebochoeridae
      • Infraorden Hippopopotamorpha
        • †Anthracotheriidae
        • Hippopotamidae Family:
      • Infraorden Cetacea:
        • Parvorden Mysticeti
          • Balaenidae family
          • Balaenopteridae
          • Family Eschrichtiidae
          • Neobalaenidae
        • Parvorden Odontoceti
          • Family Delphinidae
          • Iniidae and Platanistidae
          • Phocoenidae Family
          • Family Physeteridae
          • Kogiidae
          • Ziphiidae
          • Monodontidae family
        • Parvorden †Archaeoceti
          • † FamilyPakicetidae
          • † FamilyAmbulocetidae
          • † FamilyRemingtonocetidae
          • † FamilyProtocetidae
          • † FamilyBasilosauridae
    • Suborden Ruminantia
      • Infraorden Tragulina
        • † FamilyAmphimerycidae
        • † FamilyProdremotheriidae
        • † FamilyProtoceratidae
        • †Hypertragulidae
        • † FamilyPraetragulidae
        • Family Tragulidae
        • † FamilyArchaeomerycidae
        • † Lophiomerycidae
      • Infraorden Pecora
        • Antilocapridae family
        • Family Giraffidae
        • † FamilyClimacoceratidae
        • Family Moschidae
        • † FamilyLeptomerycidae
        • Family Cervidae
        • † Gelocidae family
        • †Palaeomerycidae family
        • † FamilyHoplitomerycidae
        • Family Bovidae