Arctic may have been evolution centre for marine mammals

Nabbing a duck and a rodent for lunch came easily to ­puijila, a creature with large, sharp teeth, a short snout and strong jaws.

But the duck and rodent also turned out to be the last meal for this slim, otter-like animal that died sometime between 20 and 25 million years ago on Nunavut's Devon Island.

In the summer of 2007, a team of scientists working on Devon Island uncovered the skeleton of an animal called puijila, a close relative of today's seals.

"What did seals look like before they had flippers? This is what we think they would have looked like," said Natalia Rybczynski, a vertebrate paleontologist with the Canadian Museum of Nature, in an interview this week.

Puijila provides the first evidence that these early members of the seal family lived in the High Arctic, said Rybczynski, who led the scientific team to Devon Island and co-authored a paper on puijila in the April 23 journal Nature.

Puijila's fossil remains also suggest that the Arctic may have been a centre of evolution for these early marine mammals, she said.

Finding puijila's skeleton was pure chance. The first bone was found after the team's all-terrain vehicle ran out of gas. Some team members started looking for fossils, while others went to fetch more fuel.

Sticking out of yellowish, ancient lake sediment was a shinbone, which then led to the discovery of the many other bones belonging to puijila and his long-ago lunch.

At first Rybczynski and her colleagues thought they had found a prehistoric otter. Then they started calling it "not-an-otter," when study revealed that the skeleton couldn't possibly be that, but another species, which had never been found before.

Puijila's full species name is puijila darwini.

Puijila, which means a "young sea mammal" in Inuktitut, is usually used in reference to a seal pup.

The Government of Nunavut's Inuit Qaujimajatuqangit Katimajiit helped select this name to recognize the people of Nunavut, Rybczynski says.

Puijila's species name, darwini, honours the British scientist Charles Darwin.

The theory of evolution developed by Darwin says complex creatures evolve from simpler ones naturally over time by "natural selection."

This passing of characteristics from one generation to the next, which help survival, can, over time, can change a dark brown grizzly bear, say, into a white polar bear or a land-dwelling carnivore like puijila into a fish-eating seal.

Puijila may be one of those "missing links" in the evolution of land mammals into marine mammals, about which Darwin wrote 150 years ago in his most famous work, "On the Origin of Species."

"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.

Puijila also gives an idea of what seals looked like before they became fully flippered, Rybczynski said.

Puijila is not a directly related to any modern seal, but a common ancestor probably gave rise to puijila and the flippered seals and walrus of today, Rybczynski said.

The next step is to see where puijila fits in the family tree and determine how puijila may have made the transition from land to sea.

Rybczynski plans a return trip to the Haughton Crater this summer to look for more fossils and to collect samples that may provide a better idea of the environment puijila lived in.

The place where puijila's skeleton was found was likely a freshwater lake, surrounded by evergreen forests some 20 million years ago.

The High Arctic climate during that period was cool, causing freshwater lakes to freeze during winter, so puijila may have also hunted by the seacoast.

The skeleton is fairly complete, so this suggests the body was not transported far after death and that puijila lived in the area and had not simply been washed in.

If you're curious to learn more about puijila, you can see the creature for yourself at the Canadian Museum of Nature in Ottawa from April 28 to May 10.

Puijila's skeleton belongs to Nunavut, but the Canadian Museum of Nature's agreement with GN allows the museum to safeguard the territory's fossil collections until there's a proper facility in Nunavut to keep and display the finds.