Sobrarbesiren

Sobrarbesiren (meaning "siren from Sobrarbe") is a genus of extinct sirenian that lived in the Eocene, about 47 million years ago. The type and only species is S. cardieli, known from a multitude of specimens from the Spanish Pyrenees. Sobrarbesiren was a medium-sized animal, long and still retaining both pairs of limbs. Although initially thought to be amphibious, later studies instead suggest that they would have been fully aquatic and been selective sea grass browsers. Unlike modern dugongs and manatees, they likely lacked a tail fluke, although it would have appeared horizontally flattened.

==Discovery and naming== thumb|left Sobrarbesiren was discovered in the Castejón de Sobrarbe-41 locality (Sobrarbe Formation) in the Spanish Pyrenees, specifically the Huesca province. The locality dates to the Lutetian stage of the Eocene and preserved 300 individual siren fossils thought to belong to at least six individuals of different growth stages. The holotype specimen is complete skull of a juvenile animal housed at the Museo de Ciencias Naturales de la Universidad de Zaragoza. Later discoveries recovered several additional specimens, including remains of young adults. Sobrarbesiren represents the first record of sirenians in western Europe as well as the first and only well preserved instance of a quadrupedal siren on the continent. Prior to its discovery, only more derived members of Dugongidae have been known from adequate remains, while any more basal fossils were only present in the form of fragments.