Scientists want to know why this croc lost its cool

A new fossil find is raising the thermostat on the Arctic's ancient climate.

A team led by John Tarduno of the University of Rochester, N.Y., has unearthed the remains of nearly 100 million-year-old champsosaurs, related to today's crocodile, on Canada's Axel Heiberg Island, a scant 600 miles from the North Pole.

Fossils have long pointed to warmer polar climates during the Late Cretaceous period, 92 million to 86 million years ago. But the evidence suggests near-freezing temperatures. Because of their similarities to modern crocodiles, fresh-water champsosaurs couldn't have survived if the average annual water temperature fell below 57 degrees F., the team holds.

Scientists are interested in this period for its lessons for the future. Its warmth has been attributed to high levels of carbon dioxide pumped into the atmosphere by volcanic activity, making it a lab for studying the effects of increased greenhouse gases on Earth's ecosystems.