Pezosiren has legs unlike the modern Manatee which has flippers. Together with fossils of later sirenians elsewhere in the world1,4,5,6,7, these new specimens document one of the most marked examples of morphological evolution … In 2001, scientists discovered the fossil of a "walking manatee," Pezosiren portelli, which had feet rather than flippers and walked on land during the Eocene epoch (54.8 million years ago to 33.7 million years ago) in what is now Jamaica. The dense and swollen ribs of prorastomids point to a partially aquatic lifestyle, as does their occur-rence in lagoonal deposits. Evolution of Early Sirenians The earliest known sirenians are prorastomids Prorastomusand Pezosiren from early and middle Eocene age rocks (50 Ma) of Jamaica (Figures 5.4 and 5.5).
The bones pulled together by Daryl Domning to construct what he named Pezosiren portelli came from five three [corrected 19Dec2017, Ed.] As a sirenian with well-developed limbs and a semi-aquatic lifestyle, Pezosiren helps demonstrate yet another (marked) example of morphological evolution in the vertebrate fossil record. Evolution cannot forever be going on someplace else". 5.2.3. Pezosiren was a pig-sized animal with a length of 2.1 m. It had a short neck, a barrel-shaped trunk, a moderate-lengthed tail and four short legs. The image shows the skeleton of the Pezosiren portelli the ancestral form of the sirenians, which has fully formed legs and the other features of modern manatees and dugongs. In order to document how these features differentiated during sirenian evolution, the ribs of 15 species, from the most basal form (Pezosiren portelli) up to extant taxa, were studied, and compared to those of other mammalian species from both morphometric and histological points of view. The global fossil re- cord for sirenians in the Eocene is much poorer, as it is also in the Oligocene and Miocene [1], and therefore new discoveries, especially well dated material in a bio- diverse and palaeoecological context, are important to our understanding of the evolution … The primitive sea cow Pezosiren portelli with a very happy Daryl Domning . I'm intrigued by the diagram next to the Pezosiren dot-point, suggesting that the relative positions of the Center of mass and Center of bouyancy have changed over the course of Sirenian evolution. (Note, in evolutionary thinking, those five metres would represent several million years worth of accumulated sediments.) [1] References: [1] "The earliest known fully quadrupedal sirenian" (Domning, 2001). separate bone beds within the five-metre thick Guys Hill Member stratum of rock in Jamaica. Pezosiren portelli is the name given to an early sirenian represented by a Jamaican fossil skeleton, described in 2001 by Daryl Domning [1], a marine mammal paleontologist at Howard University in Washington, DC.It is believed to have lived 50 million years ago, perhaps with a hippopotamus-like amphibious lifestyle, and is a perfect example of a transitional form between a land mammal and a … Pezosiren (Figure 1) [5].