Fossil reveals four-legged fish that preferred to live in water again – Revista Galileu

Fossil reveals four-legged fish that ‘came back’ to life in water (Photo: Zina Deretsky/National Science Foundation)

O Tiktaalik Roseae, a prehistoric and extinct species of four-legged fishpod fish, passed from water to land 375 million years ago and is considered a potential ancestor of land creatures. Already one of its close relatives, the newly discovered species Qikiqtania wakeichose to remain an aquatic creature rather than venture on land.

This is the finding of a new study from the laboratory of American biologist Neil Shubin, published in the journal nature, Wednesday (20). Shubin even showed the Tiktaalik in 2004, and now describes a fossil that looks very similar to the first, but with important differences. The first is the size: the Qikiqtania was small, only 80 centimeters long, and theTiktaalik could reach about 280 centimeters.

But perhaps most important, the arm of the Qikiqtania it was smooth and curved and the presence of a pectoral fin, characteristics more suited to underwater life. The uniqueness of the exotic fish’s arm bones suggests that it resumed rowing in water after its ancestors began using these limbs for walking.

“At first we thought it might be a Tiktaalik juvenile, because it was smaller and maybe some of those processes hadn’t developed yet,” Shubin said, in a report. “But your arm is smooth and boomerang-shaped, and it lacks the elements that would support it on land. It’s remarkably different and suggests something new.

The biologist collected the two species from a quarry in the northern Canadian Arctic after detecting rocks with distinctive white scales on the surface. While his team concentrated on analyzing the Tiktaalikhis brother” Qikiqtania remained unknown.

It wasn’t until fifteen years later, in 2020, that the researchers did a scan of one of the rocks and saw inside it the pectoral fin and arms different from what they had. already found. The analysis concluded that the Qikiqtania It’s a bit older than the Tiktaalik and while its pectoral fin was better suited for swimming, it did not entirely resemble a fish either.

Its shape was actually more like a curved paddle, unlike the muscular, jointed legs or fan-shaped fins we see in tetrapods (four-limbed terrestrial vertebrates) and fish today.

This finding is a counterpoint to common sense that animals evolved in a straight line that connects their prehistoric forms to a living creature today. O Qikiqtania shows that some animals took different paths, which ended up turning them off completely.

Elmer Hayward

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