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Approximately 375 million years ago, the fishapod (creatures having features of both a fish and tetrapod) Tiktaalik roseae emerged from the water to explore the land. At the same time, one of the older relatives of this species attempted a transition, got a tail and returned to the water to acquire their aquatic lifestyle, a report in Discover Magazine said.
Image Credits: Nature
Recently, an analysis of the fossil remains showed that this species transitioned to a four-legged land-living tetrapod to return to the water. This emphasized that evolution is not a linear process.
Evolution theory of land animals
According to the theory of Evolution, the characteristics of individuals help them to adapt and survive in their environment. Over time, these traits become more frequent in the population, and the population evolves. The findings of the fossilized remains of Tiktaalik roseae species revealed the evolution of fins into limbs millions of years ago.
The team of palaeontologists discovered a new species of fishapod while studying the fossils from the same archaeological area that yielded Tiktaalik. This species is similar to the first one but has developed features of swimming. Palaeontologists said these features suggested that the species’ journey onto land was short-lived.
The team named this new species Qikiqtania wakei. The discovery of this species helped them explain the early evolution of tetrapods. It also showed that evolution is not a linear process, but a path full of turns and twists that don’t result in adaptive successes.
“Tiktaalik is often treated as a transitional animal because it’s easy to see the stepwise pattern of changes from life in the water to life on land. But we know that, in evolution, things aren’t always so simple,” said Thomas Stewart, a Professor of Biology at Penn State University. “It’s more than simple transformation with just a limited number of species.”
Adapting again the aquatic lifestyle
The team found Qikiqtania at Ellesmere Island in the Canadian territory of Nunavut. It is the same place where they found Tiktaalik. The palaeontologists collected the specimens of these species and took them to their lab. But until now, they have focused more on the analysis of the Tiktaalik specimen. The smaller Qikiqtania fossils remained unanalyzed in storage.
During the analysis, the team observed that the specimen has a portion of the neck, some scales and a portion of a pair of jaws. Through computed tomography techniques (computerized X-ray imaging), they found that it also has an arm-like pectoral fin, like Tiktaalik’s and a unique humerus bone, unlike Tiktaalik’s.
“At first we thought it could be a juvenile Tiktaalik, because it was smaller,” said Neil Shubin, a Professor of Biology and Anatomy at the University of Chicago. “But the humerus is smooth and boomerang shaped, and it doesn’t have the elements that would support it pushing up on land. It’s remarkably different and suggests something new.”
The palaeontologists said that the humerus bone in Qikiqtania lacks the typical bone indicators built for walking. They concluded that the species were not adapted to survive and live on land due to their bowed shape and smooth surface. Hence, they returned to the water for their survival. “That’s what blew our minds,” said Shubin.
The detailed research has been published in the journal Nature.
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