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Apr 22, 2009 · Scientists have found the first skeleton of a land-dwelling relative of seals, sea lions, and walruses. The 20-million- to 24-million-year-old Arctic fossil sports webbed feet instead of flippers, providing a long-sought glimpse of what such animals looked like before they dove into the sea.
Molecular research placed the common ancestor between the Galapagos sea lion and California sea lion to have lived about 2.5 million years ago (Wolf, Tautz, & Trillmich, 2004). All three species are sexually dimorphic in addition to having distinctly shaped skulls with a unique sagittal crest (Sakahira and Niimi, 2007).
Apr 21, 2009 · The fossil skeleton is thought to be more than 20 million years old, making it the earliest fossil pinniped -- the taxonomic name for seals, sea lions and walruses -- yet discovered, they report in the latest issue of __Nature__.
Apr 22, 2009 · (PhysOrg.com) -- Researchers from the United States and Canada have found a fossil skeleton of a newly discovered carnivorous animal, Puijila darwini. New research suggests Puijila is a...
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Seals and sea-lions gracefully careen through today’s oceans with the help of legs that have become wide, flat flippers. But it was not always this way. Seals evolved from carnivorous ancestors that walked on land with sturdy legs; only later did these evolve into the flippers that the family is known for. Now, a beautifully new fossil called Puijila illustrates just what such early steps in seal evolution looked like. With four legs and a long tail, it must have resembled a large otter but it was, in fact, a walking seal.
Natalia Rybczynski unearthed the new animal at Devon Island, Canada and worked out that it must have swam through the waters of the Arctic circle around 20-24 million years ago. She named it Puijila darwini after an Inuit word referring to a young seal, and some obscure biologist. The skeleton has been beautifully preserved, with over 65% of the animal intact, including its limbs and most of its skull.
Puijila is a massive boon for biologists trying to understand the evolution of pinnipeds, the group that includes seals, sea lions and walruses. It’s not itself a direct ancestor, having branched off the evolutionary path that led to modern pinnipeds. It did, however, retain many of the same features that a direct ancestor would have had. “Puijila is a transitional fossil,” Rybczynski explains. “It gives us a glimpse of what the earliest stages of pinniped evolution looked like, before pinnipeds had flippers. And it suggests that in the land-to-sea transition, pinnipeds went through a freshwater phase.”
This familiar group evolved from land-dwelling carnivores and their closest living relatives are the bears and the mustelids (otters, weasels, skunks and badgers). For other marine mammals like whales and dolphins, the fossil record has given us dramatic visuals for the gradual transformation from land-dweller to full-time swimmer. But for pinnipeds, that transition is much murkier because until now, the earliest known seal Enaliarctos already had a full set of true flippers. Puijila changes all of that.
In the Origin of theSpecies, the ever-prescient Darwin 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”. This year, on the 150th anniversary of the book’s publication, the walking seal that bears his name pays a fitting tribute to Darwin’s insight.
Puijila was just over a metre in length and had a long tail. Its four legs were short but strong, and would have been attached to its trunk by powerful muscles. The bones of its toes were somewhat flattened, which strongly suggests that they were webbed. In many ways, its skeleton was very similar to a modern otter’s but the shape of its skull and teeth mark it out as a seal.
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PS: I guarantee that someone, somewhere will get these details wrong, so two points are worth clarifying:
The sea lion was reconstructed and added to an existing collection of mammals displayed in the veterinary museum of the Centre for Applied Anatomy in Bristol. This collection provides students with a variety of mammals for comparison. Our aim was to construct the skeleton as anatomically accurately as possible
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Fur seals and sea lions first appear in the middle Miocene of the North Pacific and are represented by Eotaria. Otariids diversified in the Pliocene, although they remained comparatively rare as well as small in body size, in contrast to contemporary dusignathine and odobenine walruses.
