Canadian and American fossil hunters have found the remains of strange new species in the high Arctic, a “walking seal,” that had long legs and webbed feet.
It's a transitional form that shows how seals, sea lions and walruses went from land animals to sea creatures, the researchers report in the latest edition of the British journal Nature.
They named it Puijila darwini, a combination of the Inuktitut word for young sea mammal and a tribute to Charles Darwin, 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 Rybczynskifound the bones of an animal matching that description in the Haughton crater on Devon Island in the summer of 2007.
Early seal-like creatures that had previously been found on the west coast of the United States already had flippers and were clearly at home in an aquatic environment. This animal hunted on land as well as in the water, Dr. Rybczynski says.
Seals have even teeth that are good for grasping, she says, 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 million 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.
The Haughton crater is about 20 kilometres in diameter and was created when a meteorite crashed to Earth, perhaps as much as 39 million years ago. It filled with water to become a lake. Today it is a polar desert and researchers from the National Aeronautics and Space Administration and the Canadian Space Agency have used it to test ways of living and working on Mars.
Fossils from a small rhinoceros have been found in the crater, as well as the remains of swans, fish and small deer-like creatures. Dr. Rybczynski was hoping to find other animals that lived in Arctic at a time when it was cooling down, but the discovery was serendipitous.
Their all-terrain vehicle had a faulty fuel gage, ran out of gas and got stuck in the mud. 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 Mary Dawson, Curator Emeritus with the Carnegie Museum of Natural History in Pittsburgh. They then found the jaw and limb bones spread on the surface.
When Dr. Rybczynski came back, she found Ms. Ross and Dr. Dawson doing a “fossil dance.”
“They were hopping around, wriggling in the air....It is one of these moments that just never happen.”
They knew at once they had found something unusual, and were quickly able to determine that the creature was related to modern seals, sea lions and walruses.
The discovery suggests that these animals, known as pinnipeds, may have first evolved in the Arctic, Dr. Rybczynski says.
In fact, their big eyes – which many experts believed to be an adaptation to diving into deep, dark water – may have evolved to help the animals hunt through the darkness of a long polar winter.
