Pinhead-sized mites, worms, wingless insect-like chrinomids and pintails as well as plants such as lichens evolved on the continent over millions of years rather than merely moving in when the climate warmed as widely believed.

"Antarctica's previously been seen as a barren place with just seals and penguins" which can move elsewhere when the ice shifts, he said of the report in the journal Science by scientists based in Britain and New Zealand.

"Anything else has been seen as a temporary colonist," he said. Only about 0.3 percent of Antarctica is now free of ice even in what is a warm period since the peak of the last Ice Age about 20,000 years ago.

Scientists have previously assumed that a thick lid of ice covered all the land during Ice Ages -- when ice could stretch 2,000 km (1,200 miles) out over the southern ocean -- and killed any creatures and plants dependent on land.

"This data suggests that the ice sheet is much more complex and that ice-free areas remained," he said.

GONDWANA

The study indicated that some of the pinhead-sized creatures had evolved in isolation in Antarctica since a giant continent known as Gondwana broke up 40 to 60 million years ago.

That would make pinhead-sized life forms as exotic in some ways as kangaroos in Australia, or giant tortoises in the Galapagos Islands.

Global warming, widely blamed on rising levels of carbon dioxide from fossil fuels, might threaten Antarctica's homegrown species. "Some new species are moving in," Hodgson said, pointing to grasses and marine crabs from South America.

Separately, another report in Science said rising levels of carbon dioxide were not the cause of a warming at the end of the last Ice Age, suggesting more complex links than thought between warming and the greenhouse gas.

About 19,000 years ago, deep sea temperatures warmed about 1,300 years before the tropical surface ocean and before a rise in carbon dioxide in the atmosphere, the study said.

"There has been this continual reference to the correspondence between carbon dioxide and climate change as reflected in ice core records," said Lowell Stott of the University of Southern California. "You can no longer argue that carbon dioxide alone caused the end of the Ice Ages."