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Pezosiren portelli Domning
"The Sea Cow with legs"

Over the last ten years a joint research group from Howard University, Florida Museum of Natural History and the University of the West Indies has been investigating a fossiliferous site in St. James. The site is located in the Yellow Limestone Chapelton Formation of Early Middle Eocene age and consists of alternating fossiliferous mud rocks and thin impure limestones.

The site is particularly noteworthy for the mammal fossils that it yields, which include the rhinoceros, Hyrachyrus, and a new genus and species of fossil sea cow Pezosiren portelli Domning, the latter named in the 11th October edition of Nature by Daryl Domning. This is the most complete, primitive sea cow yet discovered, and is unique to Jamaica. Pezosiren is a distant relation of the endangered Manatee that has flippers, and lives in the shallow seas around Jamaica.

Pezosiren has legs unlike the modern Manatee which has flippers.

The only other closely related fossil sea cow is Prorastomus sirenoides Owen, which is known from a skull and atlas vertebra found loose in Quashies River, Trelawny, and attributed to the Stettin Formation of Early Eocene age. The details of the legs in this form are, however, unknown.
The morphology of the skeleton of Pezosiren is comparable to that of similar-sized land mammals and indicates that Pezosiren was capable of supporting its body weight out of water. Other characteristics (such as, details of the nasal opening and the thick ribs), however, suggest that it spent much of its time in the water. This new species of sea cow represents a unique glimpse of a stage in their evolution when they made the transition from the land to the sea.

*Donations to the sea cow fund can be sent to Mr. Ian Brown, Curator, Department of Geography and Geology, University of the West Indies, Mona, Kingston, Jamaica.