While our ancestors went to land, this fishapod went back into the water
Fossils of a 400-million-year-old fishapod show it began the transition but was more adapted to water life.
As with all land-based life on Earth, our ancient ancestors evolved in our planet’s primordial seas before taking first steps onto land. For vertebrates like us, the animal associated with this evolutionary stride is the 375-million-year-old Tiktaalik roseae.
For its leap of faith into the Darwinian bible, Tiktaalik has received some tongue-in-cheek flak from internet memesters who blame the amphibious trailblazer for all of life’s modern problems.
Now, research in Nature shows a new fossil appears to have joined Tiktaalik on land – before
deciding to return to the sea, sparing its ancestors the pain of 21st century life.
Qikiqtania wakei would have been just a little over a metre in length – small compared to Tiktaalik, which could grow to nearly three metres. Though the species are similar, Qikiqtania’s body is more suited to life in water. Among the fossils are partial upper and lower jaws, portions of the neck and scales, and, importantly, a complete pectoral fin including a humerus bone lacking the muscle ridges that would indicate a limb built for walking on land.
Qikiqtania’s upper arm was smooth and curved, suggesting it spent its life paddling underwater. The unique arm bones imply that it returned to the water after its ancestors began to use their appendages for walking.
Qikiqtania’s fossils were found just days before Tiktaalik was discovered, but they were placed in storage and largely forgotten for 15 years. It was only in 2020 that a CT scan of one of the rocks revealed a pectoral fin.
“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,” explains co-author Justin Lemberg. “We could hardly believe it when the first grainy images of a pectoral fin came into view … That was in March 2020, and the university shut down all non-essential operations the following week.
“This was by no means a fascinating block at first, but we realised 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’s a fabulous story.”