Hammer found more parts of that dinosaur as well as a large sauropod, or plant-eater, resembling a diplodocus, and the new, as-yet-undescribed ornithischian.
"I don't know if we have a head, but we have a leg and a foot," he said. "It will take us a year to get a handle on what we've got."
Hammer and several fellow researchers camped at Beardmore Glacier at 6,600 feet for nearly two months. Each day fossil-hunting crews would be flown up by helicopter to the fossil beds at 12,500 feet elevation.
The new find could fill in gaps in the evolution of dinosaurs as well as the Antarctic environment, according to Thomas Holtz, professor of geology at the University of Maryland.
"This is a time when dinosaurs had just taken over," Holtz said. "They are the rabbits of the plant-eating dinosaurs: small, common, fairly fast, and they didn't have a lot of armor. They almost never show up in the movies or nobody makes plastic toys of them, but they are the stock from which the greatest plant eating dinosaurs evolved."