Protosiren (taxonomic family Protosirenidae) is an extinct early genus of the order Sirenia. Protosiren existed throughout the Lutetian and Bartonian stages of the Middle Eocene. Its geographic distribution was intercontinental: fossils have been found in the United States (North Carolina), Egypt, France, Hungary, India, and Pakistan. Like the extant sirenians (manatee and dugong), Protosiren is thought to have fed on sea grasses as well as freshwater plants. Unlike extant sirenians, Protosiren had hind limbs. Although the limbs were well-developed, they were small and the sacroiliac joint was weak. Consequently, Protosiren is thought to have been mainly aquatic.It rarely ventured on land.