ADVERTISEMENT

ADVERTISEMENT

Science

One of the first animals to land on land immediately returned to the water

ADVERTISEMENT

Written by admin

ADVERTISEMENT

ADVERTISEMENT

Approximately 365 million years ago, one group of fish left the water to live on land.

These animals were early tetrapods whose lineage would include many thousands of species, including amphibians, birds, lizards, and mammals. Humans are the descendants of those early tetrapods, and we share the legacy of their transition from water to land.

But what if they, instead of going ashore, turned back? What if these animals, as soon as they left the water, retreated to live again in more open waters?

A new fossil suggests that one fish actually did just that. Unlike other closely related animals that used their fins to support their bodies on the bottom of the water and may have ventured onto dry land from time to time, this newly discovered creature had fins designed for swimming.

Tom Stewart holding a Qikiqtania fossil. (Stephanie Sang/CC BY-ND)

In March 2020, I worked at the University of Chicago in the laboratory of biologist Neil Shubin. I worked with Justin Lemberg, another researcher in our group, on processing a fossil that was collected back in 2004 during an expedition to the Canadian Arctic.

From the face of the rock into which it was embedded, we could see fragments of jaws about 2 inches (5 cm) long, with pointed teeth. There were also areas of white scales with a bumpy texture. The anatomy has given us subtle hints that the fossil was an early tetrapod. But we wanted to look inside the rock.

So we used a technique called computed tomography, which sends x-rays through a sample to find anything that might be hidden inside, out of view.

On March 13, we scanned an unassuming piece of rock with a few scales on top and found that a whole fin was hidden inside it. Our jaws dropped. A few days later, the lab and campus closed, and COVID-19 sent us into quarantine.

Fin showed

Such a fin is very valuable. This could give scientists insight into how early tetrapods evolved and how they lived hundreds of millions of years ago. For example, based on the shape of certain skeletal bones, we can make predictions about whether an animal was swimming or walking.

Although the first scan of the fin was promising, we needed to see the skeleton in high resolution. As soon as we were allowed to return to campus, a professor in the university’s Geosciences Department helped us level the block with a stone saw.

This made the block smoother, less rocky, allowing the fin to be better scanned and viewed closer.

When the dust cleared and we finished analyzing data on jaws, scales, and fins, we realized that this animal was a new species. Not only that, it turns out that this is one of the closest known relatives of vertebrates with limbs – creatures with fingers and toes.

We called it Kikiktania Wakey. Its generic name, pronounced “kik-kik-tani-ah”, refers to Inuktitut words. Kikiktaaluk or Kikiktanithe traditional name for the region where the fossil was found.

When this fish was alive, many hundreds of millions of years ago, it was a warm environment with rivers and streams. Its specific name honors the late David Wake, a scientist and mentor who inspired many of us in the fields of evolutionary and developmental biology.

Skeletons tell how the animal lived

Kikiktania says a lot about a critical period in the history of our species. Its scales unequivocally tell researchers that it lived underwater. They show sensory channels that would allow the animal to detect the flow of water around its body.

Its jaws tell us that it foraged like a predator, biting and holding prey with a series of fangs and sucking food into its mouth.

But this Kikiktaniapectoral fin, which is most surprising. It has a humerus, just like our shoulder. But Kikiktaniahas a very unique shape.

Early tetrapods such as Tiktaalik, have humeri with a protruding ridge on the underside and a characteristic set of tubercles to which muscles attach. These bony protrusions tell us that early tetrapods lived at the bottom of lakes and streams, using their fins or arms to support themselves, first on land underwater and then on land.

Kikiktaniathe humerus is different. It lacks those signature ridges and ridges. Instead, its humerus is thin and boomerang-shaped, while the rest of the fin is large and paddle-shaped. This fin was made for swimming.

While other early tetrapods played at the water’s edge, learning what the land had to offer, Kikiktania was doing something else. His humerus is truly unlike any known.

My colleagues and I think this shows that Kikiktania turned their backs on the water’s edge and evolved to live above ground and in open water again.

Evolution is not a march in one direction

Evolution is not a simple linear process. While it may seem that early tetrapods inevitably leaned toward life on land, Kikiktania shows exactly the limitations of such a directional perspective.

Evolution did not build a ladder to humans. It is a complex set of processes that together grow into an intricate tree of life. New species are being formed and they are diversifying. Branches can diverge in any number of directions.

(Neil Shubin/CC BY-ND)

Above: Fossil finder Neil Shubin points across the valley to the site where Kikiktania was discovered on Ellesmere Island.

This fossil is special for many reasons. It’s not just a miracle that this fish was preserved in the rock for hundreds of millions of years before it was discovered by scientists in the Arctic, on Ellesmere Island. Not only is it amazingly complete, its full anatomy is revealed by a stroke of luck on the cusp of a global pandemic.

It also provides, for the first time, insight into the wider diversity and diversity of fish lifestyles as they move from water to land. This helps researchers see more than the stairs and understand this fascinating, intricate tree.

Discoveries depend on the community

Kikiktania was found on the land of the Inuit and belongs to this community. My colleagues and I were only able to carry out this research thanks to the generosity and support of the villagers of Resolute Bay and Grise Fjord, the Ivik hunters and trappers of Grise Fjord, and the Nunavut Department of Heritage and Culture.

To them on behalf of our entire research team “nakurmiik”. Thank you. Paleontological expeditions to their land have really changed our understanding of the history of life on Earth.

In the past few years, COVID-19 has prevented many paleontologists from traveling and visiting field sites around the world. We aim to return, visit old friends and search again.

Who knows what other animals are hidden, waiting to be discovered inside the unassuming stone blocks.Talk

Thomas Stewart, Associate Professor of Biology, Pennsylvania State

This article is republished from The Conversation under a Creative Commons license. Read the original article.

#animals #land #land #immediately #returned #water

ADVERTISEMENT

ADVERTISEMENT

About the author

admin

Leave a Comment