French and Tunisian scientists reported the discovery of the oldest sea cow relative found to date in the Jan. 16, 2013, open access peer reviewed journal Public Library of Science.
Sea cows (manatees, dugongs) are the only living marine mammals to feed solely on aquatic plants.
The newly discovered fossil dates from the Eocene of Tunisia and is the oldest known Sirenia clade found in Africa and predates other specimens found in Jamaica that were the previously oldest known sea cow ancestors. This animal was a fresh water mammal as opposed to present day species being salt water animals.
This discovery argues for an African origin of sea cow species. The original argument is that the sea cow species share a common ancestor with elephants. The newly described fossil is not that common ancestor.
The sea cow species are unique in that they appear to have returned to a fresh water then an ocean life after having a land dwelling series of ancestors.
The new discovery was firmly established as unique by comparison of cranial and ear anatomy with other African and Caribbean fossils that had been previously discovered.
The inner ear structure indicates the new find was strictly aquatic and fed on plants. Isotopic analysis indicates the animal occupied fresh water swamps.
Authors
Julien Benoit 1*, Sylvain Adnet 1, Essid El Mabrouk 2, Hayet Khayati 2, Mustapha Ben Haj Ali 2, Laurent Marivaux 1, Gilles Merzeraud 3, Samuel Merigeaud 4, Monique Vianey-Liaud 1, Rodolphe Tabuce 1
1 Institut des Sciences de l’Evolution, Universite´ Montpellier 2, Montpellier, France, 2 Office National des Mines, Tunis, Tunisia, 3 Ge´osciences Montpellier, Universite´ de Montpellier 2, Montpellier, France, 4 Service d’Imagerie Me´dicale de l’Hoˆ pital Lapeyronie, CHU de Montpellier, Montpellier, France
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