This 365 million year old fish fossil reveals how life came to land
About 385 million years ago during the Late Devonian period, a fish walked from the water to the shore in search of a new home. The fins are strong enough to move on land. Thus began the history of vertebrates on land.
Fast forward to 2004 in the Canadian Arctic Islands in the Nunavut Region, where researchers found two fossils about a kilometer apart. One came from the specimen that came to be known as Tiktaalik roseae (pronounced tick-TA-lick). The others resemble teenagers Tiktaalik, especially from the appearance of his jaw. But nearly 20 years after its discovery, paleontologists suspect it was something else entirely.
Researchers from the University of Chicago and Drexel University recently published a study in the journal Natural where they describe a new fish species that may have preceded Tiktaalik.
What’s new – Researchers now ascribe the second fossil to a new fish species they call Qikiqtania wake up. Pronounced “kick-kiq-TA-nee-ah,” the specimen’s name comes from the region where the fossil was found in the Qikiqtaaluk Region.
“It’s very rare to find an animal like this,” says co-author Tom Stewart Backwards. “It’s also interesting because some of the anatomy is unexpected.” He noted that some bone structures are very similar to our bodies. Stewart helped complete this research while at the University of Chicago as a postdoctoral researcher, and is now a professor of biology at Penn State University.
According to Stewart, this fossil had large pectoral muscles—or, at least one beautifully preserved chest and humerus, analogous to our arms. The team had taken X-rays of the fossils using a CT scanner, which effectively allowed them to see through the rock containing the fossils. That’s how they found the fins, pectorals and everything completely preserved.
But it wasn’t until 2020 that the team thought it might be a different species. “We spent many, many hours processing all the frameworks we could confidently say, ‘Yeah, this is something different,’” Stewart said.
Why is it important – Qikiqtania adds further nuance to how vertebrates changed and eventually became land lubbers.
“This fossil is interesting because it provides insight into a wider range of fish lifestyles in this part of vertebrate history,” Stewart said. The rarity of these fossils means that any additions will fill a gap in scientific knowledge about these fish.
Qikiqtania lacks some of the other features that characterize other fish from this time. For example, it has a large fin net to help control swimming. Like a fossil Tiktaalik more propped up on the ground with their fins either underwater or right at the water’s edge. “All of that together tells us that this might be living a different kind of lifestyle than something like Tiktaalik,” he says.
Digging details- Qikiqtania does not develop into Tiktaalik, one of.
“It’s completely normal to have two closely related animals that diverge from each other,” Stewart said Backwards. “That doesn’t mean that one came from the other.”
This is where statistical tests called phylogenetic analysis come into play. Stewart said paleontologists were interrogating a group of fossils, asking which anatomy or scales or skeletal features were the same. By constructing and visualizing how these creatures relate to one another, experts can construct a phylogeny, or “tree of life,” as Stewart puts it. At the beginning of this tree of life, Qikiqtania closely related to Tiktaalik and other Late Devonian fish fossils called Elpistostege Watsoni.
As for why these fish are changing habitats, it is still a mystery. Stewart said these creatures could have been looking for more food or fleeing predators, for example. The area was once a floodplain, so capable fish could wriggle on land and then carry floodwaters to carry them to new ponds.
What’s next – Qikiqtania belongs to the larger context of the tetrapods, which Stewart intends to refine by examining the anatomy.
“This, I think, is part of a wider series of studies trying to understand the biology, diversity, development and biomechanics of early tetrapods,” he said. “We have a new reconstruction of the postcranial skeleton of the Tiktaalik we are working on which we think is very helpful to understand how it lives and how it will move,” he said. This reconstruction can help us understand how the spine and ribs relate to the legs and other appendages.
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