Started Out as a Fish. How Did It End Up Like This?

Tiktaalik first became known to humans in 2004, after skulls and other bones from at least 10 specimens turned up in ancient streambeds in the Nunavut region of the Arctic. The discoverers, a team of paleontologists including Neil Shubin of the University of Chicago, Ted Daeschler of the Academy of Natural Sciences in Philadelphia and Farish Jenkins of Harvard University, described their findings in two Nature paper in 2006.

A local council of elders known as the Inuit Qaujimajatuqangit Katimajiit was consulted and they gave Tiktaalik its name, which translates to a large freshwater fish that lives in the shallows, in Inuktitut. The fossils have since been returned to Canada.

Scientists had been searching for a fossil like Tiktaalik, a creature on the edge of limbs for decades. And where other fossils needed a little explanation, Tiktaalik’s obvious anatomy – a fish with (almost) legs – made it the perfect icon of evolution, situated squarely between water and land.

Even then, the fossil fish hit a popular nerve and came on the heels of a Pennsylvania lawsuit that ruled against teaching creationism as an alternative to evolution in high school biology. for dr. Shubin, society’s collective desire to throw Tiktaalik back into the water is a bit of a relief: You’d only want to throw the fish out if you believed in evolution, “which to me is a beautiful thing,” he said.

When Ms. Deretsky illustrated Tiktaalik, she depicted it with its derrière submerged in water, as the back half of the fossil was a mystery at the time. But in the years since, scientists have collected more than 20 specimens and seen more of its anatomy, including its pelvis, dorsal fin and the joints of its skull.

Specifically, computed tomography scans created by Justin Lemberg, a researcher in Dr. Shubin, scientists have been able to look into rock to see the bones inside. The scans led to 3D models of the invisible parts of Tiktaalik. Some scans revealed Tiktaalik had unexpectedly massive hips (more like Thicctaalik) and a surprisingly large pelvic fin. The fish, instead of dragging itself with just its front fins, like a wheelbarrow, seemed to use all four fins to get around, like a jeep.

Other scans revealed the delicate bones of his pectoral fin. Unlike the symmetrical rays of fish fins, Tiktaalik’s fin bones were noticeably asymmetrical, allowing the joints to bend in one direction. “We think that was because these animals interacted with the ground,” said Dr. stewart.

SOURCE – www.nytimes.com

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