Qikiqtania wakei closely resembles Tiktaalik roseae — the important transitional animal considered a missing link between fish and the earliest limbed animals — but has features that made it more suited to life in the water than its famous cousin.
An artist’s reconstruction of Qikiqtania wakei (center) in the water with its larger cousin, Tiktaalik roseae. Image credit: Alex Boersma.
Qikiqtania wakei lived in what is now the Canadian Arctic some 380 million years ago (Devonian period).
It was a type of early elpistostegalian, an order of prehistoric lobe-finned fishes which lived during the Late Devonian epoch.
Qikiqtania wakei is estimated to be a standard length of 75 cm (30 inches), making it smaller than other described elpistostegalians.
Its fossilized remains were collected 1.5 km (0.9 miles) east of the site that yielded Tiktaalik roseae, but from a slightly earlier layer in the Fram Formation of southern Ellesmere Island, Nunavut, Canada.
“The specimen includes partial upper and lower jaws, portions of the neck, and scales,” said Dr. Neil Shubin, a paleontologist in the Department of Organismal Biology and Anatomy at the University of Chicago, and his colleagues.
“Mostly importantly, it also features a complete pectoral fin with a distinct humerus bone that lacks the ridges that would indicate where muscles and joints would be on a limb geared toward walking on land.”
“Instead, Qikiqtania wakei’s upper arm was smooth and curved, more suited for a life paddling underwater.”
The uniqueness of its arm bones suggest that Qikiqtania wakei returned to paddling the water after its ancestors began to use their appendages 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,” Dr. 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.”
According to the paleontologists, Qikiqtania wakei is slightly older than Tiktaalik roseae but not by much.
Their analysis of where it sits on the tree of life places it, like Tiktaalik roseae, adjacent to the earliest creatures known to have finger-like digits.
But even though Qikiqtania wakei’s distinct pectoral fin was more suited for swimming, it wasn’t entirely fish-like either.
Its curved paddle shape was a distinct adaptation, different from the jointed, muscled legs or fan-shaped fins we see in tetrapods and fish today.
“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,” said Dr. Tom Stewart, a paleontologist in the Department of Biology at the Pennsylvania State University.
“But we know that in evolution things aren’t always so simple.”
“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 findings appear today in the journal Nature.
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T.A. Stewart et al. A new elpistostegalian from the Late Devonian of the Canadian Arctic. Nature, published online July 20, 2022; doi: 10.1038/s41586-022-04990-w
Source link: https://www.sci.news/paleontology/qikiqtania-wakei-11017.html
