Tiktaalik roseae, the four-legged "fishapods" that first made the transition from water to land, has been featured in a meme. Tiktaalik is shown poking its head out of the water and ready to crawl, while an out of frame hand threatens it with a rolled up newspaper or a stick. Those of us exhausted by the modern world wish we could go back in time, shoo it back into the water, and stop evolution in its tracks, sparing us the current day of war, pestilence, and internet meme.
One of Tiktaalik's close relatives decided to go back to living in open water instead of going onto land. The laboratory of Neil Shubin, who co-discovered Tiktaalik, describes a fossil species that is more suited to life in the water than its adventurous cousin. Tiktaalik could grow up to nine feet, whereas Qikiqt wakeaniai was 30 inches long. There are parts of the neck and scales in the new fossil. It has a complete pectoral fin with a distinct humerus bone that doesn't show where the muscles and joints are on a limb geared toward walking on land. Qikiqtania's upper arm was more suited for kayaking underwater. The unique arm bones of Qikiqtania suggest that it returned to paddling the water after using its appendages for walking.
Shubin thought it could be a juvenile Tiktaalik because it was smaller. The humerus is not strong enough to push up on land. It suggests something new.
The paper "A New Elpistostegalian from the Late Devonian of the Canadian Arctic and the Diversity of Stem tetrapods" was published in Nature in July of 2022.
The project was a prehistoric one.
The fossil days before Tiktaalik was discovered were found at a site about one mile east on southernsmere Island. The traditional name for the area where the fossil site is located is Qikiqtaaluk. The wakei species is named in memory of David Wake, a renowned evolutionary Biologist from the University of California at Berkeley.
After spotting some rocks with white scales on the surface of a quarry, Shubin and his partner collected the specimen. The team focused on preparing Tiktaalik while they were in storage.
It was fifteen years after the discovery of Qikiqtania that the story began again. One of the larger rock samples was scanned in March 2020 and found to contain a pectoral fin, thanks to the work of two PhD students. It wasn't possible to get a high-resolution image because it was too deep inside the rock.
Lemberg said that the last piece they scanned was a block with only a few scales visible from the surface. We couldn't believe it when we saw the first pictures of the fin. The University shut down all non-essential operations the week after March 13th, 2020 because we didn't have the time.
In the summer of 2020 when campus facilities reopened, they contacted the Associate Professor of Geophysical Sciences, who had access to a saw that he could use to trim the specimen so that a better image could be produced. The boundaries of the block were marked by Stewart and Lemberg. The images showed a nearly complete pectoral fin and upper limb.
Shubin said that it blew their minds. When we couldn't get in the lab to see the original scans, we had to trim the block. Look at what happened when we did. We were excited to work on something during the Pandemic. The story is wonderful.
limpses into the past of animals.
It is not as old as Tiktaalik. The earliest creatures known to have finger-like digits are next to it on the tree of life. Even though Qikiqtania's fin was more suited for swimming, it wasn't like a fish. The curved paddle shape was different from what we see in fish today.
Some animals stayed on a different path that ultimately didn't work out, despite the fact that they evolved in a straight line. Those wishing Tiktaalik had stayed in the water might learn from that.
Tiktaalik is often seen as a transitional animal because it's easy to see the pattern of change from the water to the land. Stewart will be joining the faculty at Penn State University this summer. We don't see much of this part of history. We are starting to get a sense of the ecology of these animals. It's more than just a simple change with a small number of species.
More information: Thomas Stewart, A new elpistostegalian from the Late Devonian of the Canadian Arctic, Nature (2022). DOI: 10.1038/s41586-022-04990-w. www.nature.com/articles/s41586-022-04990-w Journal information: Nature
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