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New fossil fish flirted with the idea of ​​legs, but kept swimming

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About 375 million years ago, ancient fish took their first clumsy steps in shallow water and towards land. Their fins have evolved various adaptations, becoming less like fins and more like limbs. And some of these lines of fish will boldly go where there was not a single fish before, or at least where there was not a single fish before, and in millions of years will give way to vertebrates that will trample the lush kingdom of the earthly world and forever will change the world. the course of evolutionary history by inventing sherbet (ugh!) and the health insurance franchise (boo!).

Around the same time, other fish remained in place. They may even have begun to evolve to life on land, never leaving the water, developing arm bones and musculature other than the traditional fan-shaped fish fins that could help them keep themselves in shallow water. But at some point, these fish took a different path of evolution, abandoning the soil and any bottom for life in open water. They continued to swim. Unlike their famous counterparts, these fish were not among the first colonists of the earthly world. Instead, they will stay in the water and go about their business. Why uproot everything for a chance with the earth when everything is going well for you?

Now, in an article published on Wednesday in the magazine Naturea group of scientists described a new species of ancient fish, Kikiktania Wakey, did so. Although Kikiktania (pronounced “kik-kik-tani-ah”) is closely related to Tiktaaliknine-foot star of transition from water to land, Kikiktaniathe fins are more suitable for paddling than for walking. And the only copy Kikiktania much smaller – about the same length as a chow chow.

According to Sandy Cavanaugh, a researcher at George Washington University who was not involved in the new work, we humans might be tempted to think of evolution as a path to more complex, “better” species. “There is a classic notion of how humans evolve from apes, which is often misinterpreted as meaning that evolution is a “march of progress,” Kavanaugh wrote in an email. But evolution is extremely non-linear and involves a group of animals doing many different specialized things. “It’s not just an ancestor that was halfway out of the water,” said Tom Stewart, an evolutionary biologist at Pennsylvania State University and author of the new paper.

As earthly organisms, we humans can bring in our own biases, thinking that the earth is a place where anyone with a backbone can live. According to Richard Blob, an evolutionary biologist at Clemson University who was not involved in the study, while some lineages continued to evolve to land on land, other lineages continued to specialize in new ways to use water. Kikiktania “Gives a richer picture of the diverse lifestyles and body types that existed when the first vertebrates walked on land hundreds of millions of years ago,” Blob said.


Single copy Kikiktania was first discovered in 2004, less than a week before the same group of scientists discovered Tiktaalik in the neighboring area. A team of paleontologists, including Neil Shubin of the University of Chicago and Ted Dashler of the Academy of Natural Sciences at Drexel University, have been visiting the Canadian Arctic for the sixth year in a row in hopes of finding limb-tip fish. During lunch near the camp, Shubin, the author of a new newspaper, looked down and saw “a scaly field,” as he said. He came across parts of a fossil fish: parts of the jaws and scales embedded in the rock. On one stone, the size of a brick, there were only a couple of scales on the outside, and Shubin thought about leaving it. “Do I want to go back a whole block, you know, just a couple of scales?” he thought before deciding what the hell. Of course.” The team returned to the site to fully dig up the fish in the afternoon. But a few days later, the team found specimens Tiktaalik and directed all their efforts to describing the fossil, which is famous for filling the evolutionary gap between fins and legs.

Credit: Tom Stewart
Tom Stewart holds a fragment of a recently described fossil fish. Kikiktania.

More than a decade after the description of Tiktaalik, and a few months before the spring of 2020, Stewart and Justin Lemberg, then postdocs at the University of Chicago, scanned some old specimens from the Tiktaalik expeditions. On March 13, Stewart and Lemberg scanned an inconspicuous brick-sized stone with a few scales. “There was no suggestion that there was anything else,” Stewart said.

But the initial CT scan showed an image no one was expecting: “There was this beautiful fin inside,” said Lemberg, a paleontologist who is currently field researching cultural resource management in California and is the author of the new paper. The fin looked different than the Tiktaalik’s, but the scans were fuzzy, creating a dizzying array of possibilities. Perhaps the fin belonged to an infant or teenager Tiktaalik. Perhaps it came from a different species or even a different genus. “That was something we desperately wanted to explore,” Lemberg said. But a few days later, the university was closed due to the pandemic, depriving everyone from using the bulky and extremely non-portable equipment needed to better scan the block.

In the summer of 2020, researchers returned to campus. Decided to make it cleaner. In the image, Shubin performed a camouflaged handover of the block to a professor on campus, who sawed off excess pieces of stone around the fin. After several months of data processing, during which Lemberg initially transported the giant PC to his personal home, the new scans crystallized to reveal an intact 3D boomerang-shaped pectoral fin and humerus that looked completely unfamiliar to the scientists.

“When I saw the illustrations Kikiktania Wakey fossils, my jaw dropped,” Cavanaugh said, adding that she has “an unhealthy obsession with tetrapodomorph shoulder joints.” Kikiktaniathe humerus was L-shaped, as were the arm bones of other early tetrapods such as Tiktaalik. But while the humeri of all these other fishes had ridges and ridges to support the pectoral muscles necessary for supporting the body or wading on the ground, Kikiktaniathe humerus was eerily smooth. “It was more like a flipper than a hand,” Lemberg said.

On the tree of life Kikiktaniasits over a creature like Justenopteron, a fully Aquatic Devonian with a prominent ridge on the underside of the humerus. So Kikiktaniaevolutionary position shows that he lost such crests. And while Kikiktaniaclose relatives Tiktaalik, Panderichthysas well as Elpistostege all had fins and belts adapted to lean on the ground, Kikiktaniathe fin was clearly adapted for swimming, which means that the fish has returned to open water.

“We show that this boundary between water and land is actually very porous,” Shubin said. “The creatures go back and forth.”

Alice Clement, an evolutionary biologist and paleontologist at Flinders University in South Australia, who was not involved in the study, said “the CT scan is fine,” but she was cautious about interpreting the lack of ridges on the humerus as a sign that Kikiktania returned to the water. “This can only be definitively confirmed if additional material is found,” she said, noting that the species was described from a single specimen and a humerus.

KikiktaniaThe name, which comes from the Inuktitut word for the region where the fossil was found, was chosen with the help of Sylvie Leblanc, a territorial archaeologist with the Nunavut Ministry of Culture. And just like Tiktaalikfossils, Kikiktania will be returned to Canada in a few months. Stewart added that the raw data and models from the article will be publicly available. “It helps science share this data with everyone who needs it and wants it,” he said.

As with any fossil discovery, Kikiktania raises new questions about the vanished world he inhabited. Cavanaugh offered to compare Kikiktaniafin to the fins of living fish to better understand how fossil fish would move in real life. Shubin still dreams of learning more about the creatures that lived next to these Kikiktania and other early tetrapods—plants, invertebrates, and fish—that were not lucky enough to be fossilized.

Still, Kikiktania petrified by a happy accident amid the inevitable ravages of time. Stuart was amazed that KikiktaniaThe fossil contained a fish’s lateral line, a sensory system that helps the fish sense currents around its body—the only early tetrapod fossil to have such a scale preserved. “Such a fish would have a thousand scales all over its body, and there are only a small, small, small fraction of those that have features that tell us about lateral lines,” he said. “We’re lucky we found them.”

New fossil fish Qikiqtania wakei with its famous cousin Tiktaalik below.Credit: Alex Bursma
Kikiktaniacertified little Devon guy, taller than a much bigger one Tiktaalik.

#fossil #fish #flirted #idea #legs #swimming

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