Two new species of dinosaur fossils, one a quick-moving meat-eater and the other a giant plant-eater, have been discovered in Antarctica, U.S. researchers said.

The 70 million-year-old fossils of the carnivore would have rested for millenniums at the bottom of an Antarctic sea, while remains of the 100-foot-long herbivore were found on the top of a mountain.

They would have lived in a different Antarctica -- one that was warm and wet, the two teams of researchers said.

The little carnivore -- about 6 feet tall -- was found on James Ross Island, off the coast of the Antarctic Peninsula.

Not yet named, the animal probably floated out to sea after it died and settled to the bottom of what was then a shallow area of the Weddell Sea, said Judd Case of St. Mary's College of California.

Its bones and teeth suggest it may represent a population of two-legged carnivores that survived in the Antarctic long after other predators took over elsewhere on the globe.

"For whatever reason, they were still hanging out on the Antarctic continent," Case said in a statement.

A second team led by William Hammer of Augustana College in Rock Island found the 200 million-year-old plant-eater's fossils on a mountaintop 13,000 feet high near the Beardmore Glacier.

Hammer and colleagues were scouring the area for fossils after having found other new species there in the 1990s.

The animal would have been a primitive sauropod -- a long-necked, four-legged grazer similar to the better known brachiosaurs.