Pinnipeds (seals, sea lions, and walruses) are fascinating animals and a favorite at marine parks. They were one of Charles Darwin's favorite subjects for speculation, as well: in "The Origin of the Species" he wrote:
A strictly terrestrial animal, by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted in an animal so thoroughly aquatic as to brace the open ocean.
In July 2007, on Devon Island in Nunavut, Canada, a Canadian graduate student made a remarkable discovery. Elizabeth Ross stumbled upon 3-4 centimeters of a lower leg bone.
While waiting, Ross and (Photographer Martin Lipman) decided to snoop around an area they had passed every day without stopping because it lacked the kind of weathered outcroppings where fossils are typically found.
On a slope three or four metres from the stranded ATV, Ross was scuffing the ground with her boot when she saw a black shape, clearly visible among the grey and beige sand around it.
"It was right on the surface, three to four centimetres long. It was part of a lower leg bone."
Bursting with excitement, Ross clambered further up the hill to Dawson.
"I was yelling and screaming."
What they found were the remains of Pujila Darwini, a seal-like creature that exactly fulfilled Darwin's prediction.
Unlike seals and sea lions, Puijila seems to have lived more like an otter, living an active onshore life as well as life in the water.
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At first glance, Puijila's feet, legs and tail seem to belie the flippers and streamlined bodies that we see today. But closer inspection of the fossil reveals aquatic tendencies. The shape of the Puijila's forelimbs and shoulders provided power, as if the animal were a swimmer or a digger. However, it would not have been much of a digger because it had relatively small claws. It could have been a swimmer, though, because its long, flattened toe-bones are similar to those seen in some web-footed animals. These and other physical characteristics indicate the semi-aquatic nature of Puijila.