According to Dr Julien Benoit and his colleagues from the University of Science and Technology in Montpellier, France, an Eocene skull fossil discovered in Tunisia represents the oldest known ancestor of sea cows. The find supports the African origins of these marine mammals.
Manatees are sometimes called sea cow (Ahodges7 / CC BY-SA 3.0)
Some fossils of sea cow ancestors have been found in Jamaica, but the Tunisian fossil is more primitive and pre-dates these, revealing an older ancestor for sea cows that emerged at the same time as other modern mammals. The evolutionary origins of the sea cow family have been obscure.
They share an ancestor with elephants, and it is thought that their oldest relatives were terrestrial animals that gradually adapted to an aquatic life. The last common ancestor of the two species may have lived in freshwater swamps well before the time that the new species described in this study lived.
Fossil of sea cow ancestor from Djebel Chambi, Tunisia: ventral, ventrolateral and dorsal views. Scale bar = 5mm (Benoit J et al)
Though this specimen may not have been the common link between modern day sea cows and elephants, the authors’ analyses suggest that this new species lived in fresh water, not sea waters.
Dr Julien Benoit and colleagues report their find in a paper published in the journal PloS-ONE.
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Bibliographic information: Benoit J et al. 2013. Cranial Remain from Tunisia Provides New Clues for the Origin and Evolution of Sirenia (Mammalia, Afrotheria) in Africa. PLoS ONE 8(1): e54307; doi: 10.1371/journal.pone.0054307
