Online jokes about Tiktaalik roseae, the famous four-legged “fishapod” that first appeared on land 375 million years ago, have been going around throughout the pandemic. In the majority of depictions, Tiktaalik is seen sticking its head out of the water and getting ready to crawl on land as a hand out of frame threatens it with a stick or a rolled-up newspaper.
The punchline is that those of us who are weary of the modern world wish we could travel back in time and stop evolution in its tracks, saving ourselves from the current era of conflict, disease, and online memes. It turned out that one of Tiktaalik’s close cousins had done exactly that, choosing to return to dwell in the open sea rather than venture onto land.
A recent study from the lab of Neil Shubin, PhD, who co-discovered Tiktaalik in 2004, reports a fossil species that is similar to Tiktaalik but differs from it in that it was better suited to life in the water. In contrast to Tiktaalik, which could reach heights of nine feet, Qikiqtania wakei was a diminutive 30-inch creature.
The newly discovered fossil has fragments of the upper and lower jaws, the neck, and scales. Most critically, it has a complete pectoral fin and a humerus bone that is distinct and devoid of the ridges that would identify the location of muscles and joints on a limb designed for walking on land.
The top arm of Qikiqtania was smooth and curved, more adapted to a life spent paddling underwater. The peculiarity of Qikiqtania’s arm bones suggests that it resumed water paddling after its predecessors started using their limbs for walking.
“At first we thought it could be a juvenile Tiktaalik, because it was smaller and maybe some of those processes hadn’t developed yet,” Shubin said. “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 paper, “A New Elpistostegalian from the Late Devonian of the Canadian Arctic and the diversity of stem tetrapods,” was published July 20, 2022, in Nature.
That’s what blew our minds. This was by no means a fascinating block at first, but we realized during the COVID lockdown when we couldn’t get in the lab that the original scan wasn’t good enough and we needed to trim the block. And when we did, look at what happened. It gave us something exciting to work on during the pandemic. It’s a fabulous story.
Neil Shubin
A prehistoric pandemic project
The fossil was discovered by Shubin, the Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy at the University of Chicago, at a location about one mile east on southern Ellesmere Island in the territory of Nunavut in northern Arctic Canada, days before Tiktaalik was found.
The Inuktitut word Qikiqtaaluk or Qikiqtani, the traditional name for the area where the fossil site is located, is where the name Qikiatania originates. In honor of the late David Wake, a renowned evolutionary biologist from the University of California in Berkeley, the species name wakei was given.
After discovering a few interesting-looking rocks with distinct, white scales on the surface, Shubin and his field colleague Ted Daeschler, PhD, from the Academy of Natural Sciences of Drexel University, went to a quarry and collected the specimens there. But as the team concentrated on preparing Tiktaalik, they remained mainly untouched in storage.
The discovery of Qikiqtania became the subject of another pandemic myth fifteen years later. In March 2020, postdoctoral scientists Tom Stewart, PhD, and Justin Lemberg, PhD, CT-scanned one of the larger rock specimens and discovered that it featured a pectoral fin.
Sadly, they were unable to obtain a high-resolution image of it because it was too deep into the rock, and as the epidemic forced labs to close, they were also unable to do much more with it.
“We were trying to collect as much CT-data of the material as we could before the lockdown, and the very last piece we scanned was a large, unassuming block with only a few flecks of scales visible from the surface,” said Lemberg, who is now doing cultural resource management fieldwork in Southern California.
“We could hardly believe it when the first, grainy images of a pectoral fin came into view. We knew we could collect a better scan of the block if we had the time, but that was March 13th, 2020, and the University shut down all non-essential operations the following week.”
They got in touch with Mark Webster, PhD, Associate Professor of Geophysical Sciences, who had access to a saw that could remove portions from the specimen so that a CT scanner could come closer and produce a better image, in the summer of 2020 when campus facilities reopened.
In order to facilitate an exchange, Stewart and Lemberg meticulously delineated the block’s boundaries and set up shop outside their lab in Culver Hall. The resultant photos showed a virtually whole upper arm and pectoral fin, including the recognizable humerus bone.
“That’s what blew our minds,” Shubin said. “This was by no means a fascinating block at first, but we realized during the COVID lockdown when we couldn’t get in the lab that the original scan wasn’t good enough and we needed to trim the block. And when we did, look at what happened. It gave us something exciting to work on during the pandemic. It’s a fabulous story.”
Glimpses into vertebrate history
Tiktaalik and Qikiqtania are only somewhat older than one another. According to the team’s examination of its position on the evolutionary tree, it, like Tiktaalik, is situated close to the oldest known organisms with finger-like digits.
Qikiqtania had a distinctive pectoral fin that was more suited to swimming, but it wasn’t fully fish-like. Different from the jointed, muscled legs or fan-shaped fins we see in modern tetrapods and fish, its curving paddle shape was a distinctive adaption.
The Qikiqtania demonstrates that some animals continued on a different course that eventually didn’t work out, contrary to the common belief that animals evolved in a straight line from their prehistoric beginnings to some living creatures today. For those who wished Tiktaalik had remained in the sea with it, perhaps this serves as a lesson.
“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 Stewart, who will be joining the faculty at Penn State University this summer.
“We don’t often get glimpses into this part of vertebrate history. Now we’re starting to uncover that diversity and to get a sense of the ecology and unique adaptations of these animals. It’s more than simple transformation with just a limited number of species.”
The research was supported by the Brinson Foundation, the Academy of Natural Sciences of Drexel University, the University of Chicago Biological Sciences Division, the Polar Continental Shelf Program of Natural Resources Canada, the Nunavut Department of Culture and Heritage, the Hamlet of Grise Fiord and its Iviq Hunters and Trappers Association, and the National Science Foundation.
