Arctic fossil points to missing link between seals and land mammals
Last Updated: Wednesday, April 22, 2009 | 3:36 PM CT
CBC News
Canadian Museum of Nature researcher Natalia Rybczynski and her team found an early pinniped fossil skeleton, including part of the skull, shown here, in a former lake on Devon Island, Nunavut. (Martin Lipman/Canadian Museum of Nature)The fossil remains of a flipper-free mammal related to modern seals have been discovered in Nunavut by Ottawa researchers who stumbled upon them after their ATV ran out of gas.
Natalia Rybczynski, a paleontologist at the Canadian Museum of Nature, and her research team found the first bone of the ancient pinniped — the scientific group that includes seals, sea lions and walruses — while waiting for other team members to return with a jerry can of fuel during an expedition to a former crater lake on Devon Island in 2007.
The findings from the study, published in Thursday's edition of Nature, suggest pinnipeds evolved in the Arctic from freshwater animals.
"It fills the gap between the land-living ancestor and the flippered seal-like animal that we see around us today," Rybczynski said Wednesday. (CBC radio's Quirks and Quarks has an interview with Dr. Rybczynski, air date April 25).
An artist's conception shows Puijila darwini as otter-like, with a long tail and webbed feet. (Mark A. Klingler/Carnegie Museum of Natural History)The animal had a long, streamlined body with heavy limbs, suggesting it had well-developed muscles. It had a long tail and likely moved much more easily over land than modern seals. It was little longer than a cat from the tip of its nose to the tip of its tail (about 110 centimetres). It didn't have flippers, but had flattened digits that suggest webbed feet. Its canine teeth were large, indicating a meat eater, and it had a short snout and muscular jaw.
Previously, the earliest pinniped skeleton ever found was a saltwater animal with flippers found on the northern Pacific shores of North America, said a news release from the Carnegie Museum of Natural History in Pittsburgh, which collaborated on the project.
Because Charles Darwin, who first suggested the theory of natural selection, suggested that some marine animals may have evolved from freshwater ancestors, the researchers named their new find Puijila darwini.
23 million years old, researchers believe
The researchers said the first part of the seal's scientific name, Puijila, is an Inuktitut word meaning "young sea mammal," which is often used to refer to seals and was given to the animal after consultation with the government of Nunavut.
Rybczynski originally went up to Devon Island to hunt for clumps of peat moss, sand and tree trunks for research on climate change.
About 65 per cent of the animal's skeleton was found, as illustrated by this 3-D model reconstruction. The brown areas represent the fossil bones that were found. (Alex Tirabasso/Canadian Museum of Nature)Running out of gas was just one of the many challenges she faced, along with more dramatic difficulties such gusts of wind so strong they carried away her tent and all her gear.
When the ATV ran out of fuel, Liz Ross, a summer student on the expedition, was left with the vehicle about a kilometre from camp.
"I was a little upset with myself for not checking the gas level so I was kind of scuffing my toes in the dirt and as I looked down, there was a black piece of bone," said Ross, who was studying at Ottawa's Carleton University at the time.
It later proved to be part of a Puijila leg bone.
After its 2007 discovery, the researchers returned to the site in 2008 and between the two visits managed to find about 65 per cent of the skeleton, an amount considered by the researchers as "surprisingly complete."
At first, the researchers thought the fossil bones were part of a prehistoric otter, but analysis at the museum's labs in Gatineau, Que., showed that could not be the case, said a news release from the Museum of Nature.
Rybczynski did further analysis with researchers at the Carnegie museum and the American Museum of Natural History and determined the animal was most closely related to pinnipeds.
The researchers estimate that the ancient seal lived about 23 million years ago in the early part of a period called the Miocene.
Fossil pollen suggests that at that time, Devon Island was warmer than it is today, with a climate similar to the northeastern U.S., and was covered in trees such as larch, alder, spruce, fir, pine, birch, chestnut and sweetgum.
Based on the fact that the Puijila skeleton was so complete, the researchers think the animal died close to where it was found, in the crater lake, which appears to have been freshwater, based on the fossils of fish that lived there. When the lake froze in the winter, the animal would likely have had to travel over land to the sea for food, suggests a news release from the Carnegie Museum of Natural History.
Because Puijila lived at around the same time as some flippered pinnipeds, the researchers believe it was not the ancestor of modern seals, but that Puijila and seals shared a common pinniped ancestor.
The skeleton will be on display at the Canadian Museum of Nature in Ottawa from April 28 to May 10.
