A fossil from 385 million years in the past named Qikiqtania wakei exhibits {that a} descendant of early land animals misplaced its variations for land and have become a extra environment friendly swimmer


20 July 2022

Illustration of Qikiqtania wakei in the water

Illustration of Qikiqtania wakei (centre) within the water with its bigger relative, Tiktaalik roseae

Alex Boersma

A scaly, finned creature that lived in water 385 million years in the past descended from four-legged land animals, in a transparent instance of a “backward” step in evolution.

Some fish grew legs and developed the flexibility to face practically 400 million years in the past, beginning the evolutionary lineage of four-legged animals referred to as tetrapods. However the clean limb bones of the newly described Qikiqtania wakei fossil couldn’t have supported the muscular tissues wanted for standing, that means the “fishapod” had advanced again right into a swimming, full-time water dweller, says Neil Shubin on the College of Chicago.

“The ancestors of Qikiqtania had been already taking these steps [out of water], however this was a creature that stated, ‘I’m not doing that, I just like the water higher!’” he says. “It was, mainly, the relative that went again.”

Shubin and his colleagues unearthed the scaly Qikiqtania fossil embedded in rock within the Canadian Arctic Archipelago in 2004, on the similar time and in practically the identical place as their discovery of Tiktaalik roseae, a fishapod representing the evolutionary transition from fish to amphibian.

Scans of Qikiqtania – which was most likely about 75 centimetres lengthy when it was alive – revealed components of the higher and decrease jaw that counsel it might feed by sucking in prey, like Tiktaalik did, says Shubin. It additionally had fangs and enamel that had been “like steak knives”, indicating the animal might chew as effectively.

Qikiqtania is clearly a detailed relative of Tiktaalik, however the humerus bone in its pectoral fin is comparatively clean and boomerang-shaped, which might have made it unlikely to stroll and even stand. This meant that it was neither a fish that had by no means walked, nor a fishapod that was presently strolling.

“It had misplaced all these processes and cabinets on the humerus and all these locations the place muscular tissues would connect that will have allowed it to push up,” says Shubin.

As an alternative of reverting to the physique of its extra primitive water-dwelling ancestors, Qikiqtania had advanced to turn out to be an much more environment friendly swimmer in open waters, with fins considerably like ping-pong paddles. “What’s fascinating about it’s that it went again and have become tremendous specialised,” says Shubin.

The workforce named the animal for Qikiqtani, the Indigenous phrase for the area the place the fossil was discovered, and for David Wake, an evolutionary biologist on the College of California at Berkeley who died in 2021.

The findings spotlight the truth that evolution isn’t all the time a simple course of, says Shubin. “This can be a vivid instance of not solely simply going again, however going again in a complete new manner,” he says. “And it’s a real shock if you see it in such a dramatic style.”

Journal reference: Nature, DOI: 10.1038/s41586-022-04990-w

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