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Mar 20, 2024 · A prehistoric seal that lived along an ancient shore where waves, scavengers and other processes break down a body was much less likely to be preserved in the fossil record than a marine mammal...
- Riley Black
- Overview
- More on transitional fossils:
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:
Sources:https://www.nationalgeographic.com/science/article/puijila-the-walking-seal-a-beautiful-transitional-fossilhttps://royalsocietypublishing.org/doi/10....
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- Animal Origins
In other words, Puijila is a transitional fossil that provides information about how the seals returned to the sea, similar to how Archaeopteryx illuminates the origin of birds.
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.
May 24, 2024 · From first appearing around 30 million years ago, seals have spread around the world to become one of the most successful marine predators alive today. Seals are mostly found in the colder waters of the northern and southern hemispheres. There are 34 surviving species of seals, also known as pinnipeds, and these are split up into three main groups.
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Oct 15, 2022 · Increasing predation pressure by pinnipeds through the late Cenozoic drove Nautilus into its present-day refuge in the deep tropical Indo-West Pacific Ocean . Above: Reconstruction of the fossil Nautilus taiwanus inhabiting deeper waters of the tropical Indo-West Pacific Ocean about 20 million years ago. Illustration by Cheng-Han Sun.
