Fossil Carnivore Sheds Light on Pinneped Evolution

A small fossil carnivore discovered on Devon Island, in Nunavut, Canada has shed light on an obscure stage in pinneped evolution. Pinnepeds belong to a group of marine carnivores that includes seals, sea lions, and the walrus. Pinnepeds are semi-aquatic mammals with limbs that have been modified into flippers. Pinnepeds are believed to be close cousins to two other groups of carnivores, the Ursidae (bears) and the Mustleoidae (skunks, otters, badgers, and relatives). Although scientists understand a considerable amount about the relationship pinnepeds have to other groups of carnivores, little is know about the terrestrial ancestors of today's pinnepeds.

The new fossil is described in detail by Natalia Rybczynski (Canadian Museum of Nature), Mary Dawson (Carnegie Museum of Natural History), and Richard Tedford (American Museum of Natural History) in a paper published in the April 2009 issue of Nature. The fossil has been given the scientific name Puijila darwini. The first part of the creature's scientific name, Puijila, is the Inuktitut word meaning "young sea mammal". The second part of the name, darwini, refers to Charles Darwin who wrote:

"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." ~ Charles Darwin, On the Origin of Species by Means of Natural Selection

Puijila darwini had a number of characteristics that would have suited a terrestrial lifestyle: a long tail and long front and back limbs. Puijila darwini also exhibited a number of adaptations that hinted at a semi-aquatic lifestyle, most notably flattened finger bones that indicate possible webbed feet.

Find out more:

• Fossil Evidence of Missing Link in the Origin of Seals, Sea Lions, Walruses Found in Canadian Arctic (Eurekalert)
• Rybczynski, N., Dawson, M., & Tedford, R. (2009). A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia Nature, 458 (7241), 1021-1024 DOI: 10.1038/nature07985

Photo © Mark A. Klingler / Carnegie Museum of Natural History.