What is "pezosiren"

Pezosiren portelli is a basal sirenian from the early Eocene of Jamaica, 50 million years ago. The type specimen is represented by a Jamaican fossil skeleton, described in 2001 by Daryl Domning, a marine mammal paleontologist at Howard University in Washington, DC. It is believed to have a hippopotamus-like amphibious lifestyle, and is a perfect example of a transitional form between a land mammal and a sea mammal.

P. portelli had the typical skull and basic body shape shared by most modern sirenians, like manatees and dugongs, but also had four limbs, not yet modified into flippers, with well-developed feet and hands, that were still adapted for walking on land.