Prorastomus sirenoides

Prorastomus is among the earliest of the sirenians, dating back to the Middle Eocene.  It was a fairly small member of the order, growing to a maximum length of about 1.5 meters (5ft) in length.  Unlike modern sirenians, it was not fully aquatic and had four fully functional limbs.  It likely had a similar lifestyle to hippos, and like all sirenians, it was a herbivore.  It's remains were uncovered in Jamaica.