SCIENCE REPORTER
Canadian and American fossil hunters have found the remains of a strange creature in the High Arctic they say is a "missing link" that the great naturalist Charles Darwin speculated about 150 years ago.
The "walking seal" had long legs and webbed feet and was a transitional form that shows how seals, sea lions and walruses went from land to sea, the researchers report in today's edition of the journal Nature.
They named it Puijila darwini, a combination of the Inuktitut word for young sea mammal and a tribute to the visionary scientist who predicted the existence of such a creature in his seminal book about evolution.
"A strictly terrestrial animal, by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted into an animal so thoroughly aquatic as to brave the open ocean," Darwin wrote in On the Origin of Species by Means of Natural Selection, which was first published 150 years ago.
An expedition led by Canadian Museum of Nature paleontologist Natalia Rybczynski found the bones of an animal that matches that description in the Haughton crater on Devon Island in the summer of 2007.
Early seal-like creatures that have previously been found already had flippers. This animal hunted on land as well as in the water, Dr. Rybczynski said. Seals have even teeth that are good for grasping, she said, but Puijila had a mouth more like a dog or a fox.
It was found in the sediments of what was once the bottom of a freshwater lake. At the time, the Arctic was forested with a temperate climate. The lake would have frozen in the winter, so the scientists say it is likely Puijila travelled over land to find food in the ocean.
It is estimated to be between 20 and 24 million years old. Seals had evolved by then, so it would have been a living fossil, an ancestral form that remained unchanged while its relatives became more adapted to the sea.
Fossils from a small rhinoceros, swans and fish have been found in the Haughton crater, which is about 20 kilometres in diameter and was created when a meteorite crashed to Earth.
Dr. Rybczynski was hoping to unearth other animals, but the discovery of the walking seal was serendipitous.
The researchers' all-terrain vehicle had a faulty fuel gauge. It ran out of gas and got stuck in the mud, so while Dr. Rybczynski trudged back to the base camp for more fuel, Carleton University student Elizabeth Ross starting poking around. She found a small black bone that she showed to another team member, Mary Dawson, an emeritus curator with the Carnegie Museum of Natural History in Pittsburgh. They spotted the jaw and limb bones spread on the ground, and knew at once that they had found something unusual.
"It is one of these moments that just never happen," Dr. Rybczynski said.
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PALEONTOLOGY
Capable of hunting on land or in the sea, Puijila darwini is considered a 'missing link' through which seals, sea lions and walruses evolved from land animals to sea creatures.
PUIJILA DARWINI
SWAM IN THE OCEAN ...... AND WALKED ON LAND
Mouth is characteristic of a terrestrial predator, such as a fox
Large eyes may have evolved to help Puijila hunt in polar winters
Webbed feet propelled Puijila through the water
20-24 MILLION YEARS AGO
The Bering land bridge stopped marine life from mixing between the North Atlantic and North Pacific Oceans. But Puijila would have been able to spread south in both directions, giving rise to seal-like creatures worldwide.
FOSSIL FIND
Fossil discovered at Haughton crater...DEVON ISLAND
THE GLOBE AND MAIL
ANIMAL ILLUSTRATIONS: STEFAN THOMPSON
SOURCE: NATURE