Tiny fossils have helped refine the timing of the climate shift that gave rise to Antarctica's remarkable Dry Valleys, a landscape akin to Mars.
The famously ice-free terrain enjoyed more benign, tundra-like conditions 14 million years ago - but then flipped to the intensely cold setting seen today.
Scientists tell a Royal Society journal that ancient lake-living shrimp-like creatures can pinpoint the big switch.
The ostracods would not have coped with a harsh, dry environment, they say.
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