The discovery of an 85-million-year-old plesiosaur has pushed back the marine reptile's presence in Antarctica by 15 million years. (See prehistoric sea-monster pictures.)

"The fragments we found don't belong to any group registered on the continent before, which indicates a greater diversity of the plesiosaurs in Antarctica than previously suspected," said team leader Alexander Kellner, of the National Museum of Brazil at the Federal University of Rio de Janeiro.

Fragments of the vertebrae, head, and flippers suggest the newfound plesiosaur was 20 to 23 feet (6 to 7 meters) long. The bones weren't, however, enough to identify the species of the plesiosaur.

Plesiosaurs roamed the seas worldwide between about 205 million to 65 million years ago,