Tethytheria

Tethytheria is a step in the evolution of elephants, it belongs to the Paenungulata and includes Proboscidea (the trunk animals), Sirenia (seacows, manatees and dugongs) and their common ancestor.

After being land animals, they became aquatic or semiaquatic animals. They were not alone, several types of mammals returned to the water. The reason was probably food: so much of the earth was covered with swamps and lakes, with water plants for the vegetarian species in Tethytheria.

The elephants and the sirenians has two milk glands between the forelimbs and their molars are developing from behind, pushing the older out and replacing them with a new set, and their insicives are dominant.

(Picture: "Diving pig, by Michael Sowa. Buy at AllPosters.com)

Recent immunological and molecular evidence shows an extremely close affinity between present-day elephants and the aquatic Sirenia (dugong and manatees). Some of their common ancestors must have developed into fully aquatic animals, who later returning to land. Even recent elephants show, especially during their embryonic phases, but even after, typical caracters that they share with aquatic animals, like the manatees.

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Those caracters includes: Testes inside the body, located near the kidneys Female sexual organs inbedded in the body, protected with a vestibule Hairless bodies with a thick layer of subcutane fat to isolate Breathing is only performed through the nostrils, so the animals can open the mouth and feed under water Wrinkled skin, in order to minimize dehydration, when not in water Nephrostomes, (a feature of aquatic vertebrates) in the mesonephric kidneys at all stages of development

Taxonomy

• Mammalia - (class)
  • Theria - (subclass)
    • Eutheria - (metaclass placentals)
      • Paenungulata
      - (superorder)
      • Tethyteria - (Proboscideans and sirenians)
        • Sirenia
        • Proboscidea - (order)
          follow this line to the elephants!!

OutLink: The developing renal, reproductive, and respiratory systems of the African elephant suggest an aquatic ancestry (Gaeth, Short, and Renfree, University of Melbourne, Parkville, Victoria 3052, Australia)

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