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November 8, 2026

Findivoza

Science & Health

Tiny fossil fish from Alberta rewrite the story of the fish in our rivers today

Faizan Altaf

Sixty-six million years ago, in the rivers of what is now central Alberta in Canada, tiny fish swam through fresh water while Tyrannosaurus rex walked the land nearby. They were only a few centimetres long, and when they died their bodies settled into dark mud and turned to stone. For decades, scientists could barely study them, because the fossils were locked inside black rock and showed almost nothing to the naked eye.

Now a team of Canadian researchers has used ultrabright synchrotron light to look inside those fossils without breaking them apart. What they found has changed what scientists thought they knew about two great groups of fish. One is a relative of the beardfish, a group that today lives only in the deep ocean. The other belongs to the percomorphs, the huge group that includes perch, bass, gobies and mackerel. The study shows that both groups were already living in North American fresh water before the asteroid struck and ended the age of the dinosaurs.

The research, led by Alison M. Murray and published in the Canadian Journal of Zoology, is based on rare, complete fossil skeletons from a site with a fitting name: Pisces Point, in central Alberta. The work was reported by the Canadian Light Source on 27 October 2026, and the findings were widely reported on 30 October 2026.

At a glance

What happened: Researchers used synchrotron light to study complete fossil fish skeletons from Pisces Point in Alberta, and identified a beardfish relative and an early percomorph living in fresh water 66 million years ago.

Why it matters: It shows that two major groups of modern fish were already in rivers, not only in the sea, before the dinosaur-ending asteroid struck — and it fills a long-standing gap in the story of freshwater fish.

What happens next: The team can now use the same imaging method on other small fossils from the site, and compare the ancient bones with isolated fossil jaws found across North America.

A site named for its fish

Pisces Point is a fossil site in the Scollard Formation of central Alberta. The rocks there date to the Maastrichtian, the final stage of the Cretaceous period, the last chapter of the age of the dinosaurs. The site was named to reflect the diversity of complete, articulated fish being recovered from it — articulated meaning that the bones of each fish are still joined together in the shape of the animal, rather than scattered.

That is what makes the site so unusual. Most freshwater fish fossils from this period are single, isolated bones: a jaw here, a tooth there. Donald Brinkman, an emeritus researcher at the Royal Tyrrell Museum and an adjunct professor in the University of Alberta’s Department of Biological Sciences, explained the problem. “Freshwater fossils are almost all isolated individual bones like jaws, and these are very difficult to work with taxonomically,” he said. “There are very few full skeletons, which is ideally what we want, to know what kind of fish it is and its relationship to modern groups.”

Pisces Point has already produced a remarkable cast of characters. Earlier work at the site described a new fish called Wilsonichthys aridinsulensis, a relative of the bony-tongued fishes, and a small percopsiform fish named Lindoeichthys albertensis in 2019. The new study adds two more fish to that list, and both of them matter far beyond Alberta. The researchers come from the Royal Tyrrell Museum, the University of Alberta and Western University.

Seeing inside black rock

The fossils at Pisces Point are very small — just a few centimetres long — and they are embedded in black rocks. That combination makes them almost impossible to study by eye. “We studied the full articulated specimens, so the whole fossilized fish was there,” said Van Loon, an adjunct professor in Western University’s Departments of Earth Sciences and Anthropology. But seeing the detail inside the dark stone needed something far more powerful than a microscope.

The team turned to the Canadian Light Source, a synchrotron facility at the University of Saskatchewan. A synchrotron produces extremely bright light, far brighter than an ordinary X-ray machine, which scientists can use to peer inside solid objects. In this case, it let the researchers see the shape and internal structure of the tiny skeletons in far more detail than they otherwise could.

Just as importantly, the method let them work digitally. “It allowed us to see the morphology of the skeletons in far more detail than we otherwise could, as well as digitally dissect out individual parts like the jaw to compare with the isolated bones,” Brinkman said. The team could take a virtual jawbone out of a complete fossil fish and hold it up, on screen, against the isolated fossil jaws collected from sites across North America for decades.

That comparison is the key to the whole study. Isolated jaws and teeth are the most common freshwater fish fossils from the Late Cretaceous, but on their own they are hard to identify. Once scientists know what the jaw of a particular fish looks like in a complete skeleton, they can go back through museum drawers and recognise the same fish from a single bone. The approach also protects the fossils themselves: the specimens are rare and fragile, and imaging leaves them untouched while revealing what is hidden within the rock.

The deep-sea fish that once swam in rivers

The first of the two fish at the centre of the study is a polymixiiform, a member of the order Polymixiiformes. The researchers focused on two fish from the extraordinarily diverse group known as acanthomorphs, or spiny-rayed fish, which make up around one-third of all living vertebrates. Their modern relatives include tuna in the oceans and perch in fresh water.

Polymixiiforms are better known by their everyday name: beardfish. They are named for the pair of long, whisker-like barbels under their chins. Today, beardfish are creatures of the deep sea. The only living genus is Polymixia, with 12 species, and they are all bottom-dwelling marine fish found in tropical and subtropical waters of the Atlantic, Indian and western Pacific oceans, down to depths of about 800 metres. Most are relatively small, although one species grows to more than 40 centimetres long. Because they are the only survivors of a once-diverse order, they are often described as living fossils.

The Alberta fossil tells a different story about where this group once lived. The new fish has been named Elnorichthys pennockae, and the paper tentatively places it in the extinct family Boreiohydriidae. It is the earliest member of a group that now lives only in the deep ocean — and the new research shows that it lived in fresh water during the Cretaceous period.

That is a striking change of address. A group whose modern members never leave the deep sea was, 66 million years ago, swimming in the rivers of North America. Many different fossil families and genera of beardfish are known from the Late Cretaceous and the early Cenozoic, the era that followed the extinction of the dinosaurs. Today, only a single genus remains, confined to the deep ocean.

The second fish, and the rise of the percomorphs

The second fish in the study is a member of the percomorphs, and it may be the more important of the two. According to the researchers, this specimen is the earliest evidence of percomorphs in the Cretaceous period.

Percomorphs are the largest order of teleost fishes, the group that contains most of the bony fish alive today. Britannica describes them as typically small to moderate in size, with streamlined bodies, and notes that the group includes well-known fish such as perches, basses, gobies, mackerels and blennies. They live in almost every aquatic habitat on Earth, from coral reefs to mountain streams, and they include some of the world’s most important food fish, including tuna and mackerel.

Finding the earliest percomorph in a freshwater deposit in Alberta matters because it pushes the group’s history further back and into a new habitat. Until now, the early history of percomorphs has been pieced together mainly from marine fossils. A freshwater percomorph from the end of the Cretaceous shows that the group had already spread beyond the sea before the asteroid struck.

The percomorph specimen is described in the paper as a fish of uncertain relationships within the group. But its anatomy is clear enough to place it among the percomorphs, and that alone is enough to change the timeline. It shows that the group that would come to dominate the world’s waters — salt and fresh alike — was already diversifying in rivers while dinosaurs still walked the banks.

Why a few centimetres of bone matter

Taken together, the two new fish carry a bigger message than either one alone. With the percopsiform Lindoeichthys albertensis already known from the same site, Pisces Point now shows at least three distantly related spiny-rayed lineages living in North American fresh water by the end of the Cretaceous.

The study also changes how scientists read the rest of the fossil record. Now that the team has matched complete skeletons to their jaws, researchers can revisit the isolated bones collected from other Late Cretaceous sites and identify them with new confidence.

“These fossils have provided information about the diversity and evolutionary history of these groups of fish in particular,” Brinkman said. “It’s providing information on the history of life — what were the steps leading to where we are today?”

Life on the edge of extinction

The timing of these fossils gives them an extra poignancy. They come from the very end of the Cretaceous, just before one of the worst days in the history of life. Sixty-six million years ago, an asteroid between 10 and 15 kilometres wide struck what is now the Yucatán Peninsula in Mexico, blasting out the Chicxulub crater, which is about 150 kilometres across. The impact ended the dinosaurs’ reign, which had lasted 180 million years.

The Natural History Museum in London explains that around 75 per cent of Earth’s animals died out in the extinction that followed, including all non-bird dinosaurs, the flying pterosaurs, the great marine reptiles and the ammonites. All land animals weighing more than 25 kilogrammes died out. Plants fared better than animals, because their seeds and pollen can survive harsh periods for longer.

Yet many of the major animal groups alive today were already in place before the asteroid hit, and the lines that led to modern animals got through. Birds are the living dinosaurs. And in the rivers, small fish like the ones at Pisces Point survived to become the ancestors of the fish we know today.

The Alberta fossils therefore capture a world on the brink: a diverse freshwater community in the last moments before a catastrophe. Some of those experiments survived. The percomorphs went on to become the most diverse group of fish on the planet. The beardfish did not — they retreated to the deep sea, where a single genus survives today.

What happens next

The study, published as “Early diversity of acanthomorph fishes in fresh waters of the Late Cretaceous” in volume 104 of the Canadian Journal of Zoology, runs to 18 pages. But the work at Pisces Point is far from finished. The site holds an abundance of complete fossil fish skeletons, and only a fraction have been studied in detail so far.

The synchrotron method used in this study can now be applied to other specimens from the site, including fish whose identities are still unknown. Each new skeleton adds another piece to the picture of the Late Cretaceous river community, and each one helps scientists identify the isolated bones found at other sites across the Western Interior of North America.

Frequently asked questions

What exactly did scientists find in Alberta?

They studied complete fossil skeletons of two small fish from Pisces Point in central Alberta, in rocks from the end of the Cretaceous period, about 66 million years ago. One is a beardfish relative named Elnorichthys pennockae; the other is an early percomorph, a member of the group that includes perch, bass and mackerel.

Why is Pisces Point special?

Most freshwater fish fossils from this period are single isolated bones, such as jaws, which are hard to identify. Pisces Point preserves whole, articulated skeletons, with the bones still joined together. That lets scientists identify the fish and work out how they are related to modern groups.

How did scientists study fossils hidden in black rock?

They used the Canadian Light Source, a synchrotron facility at the University of Saskatchewan. Its ultrabright light let them see inside the tiny skeletons without breaking the fossils apart, and digitally remove parts such as the jaw for comparison with isolated bones.

What is a beardfish, and where does it live today?

Beardfish are deep-sea fish named for the pair of long barbels under their chins. The only living genus is Polymixia, with 12 species, all bottom-dwelling marine fish found in tropical and subtropical waters down to about 800 metres deep. The Alberta fossil shows their relatives once lived in fresh water.

What are percomorphs?

Percomorphs are the largest order of teleost fishes, the group containing most bony fish alive today. They include perches, basses, gobies, mackerels and blennies, and they live in almost every aquatic habitat on Earth. The Alberta specimen is described as the earliest evidence of percomorphs in the Cretaceous period.

Why does this discovery matter for fish today?

It shows that two major groups of modern fish were already living in rivers, not only in the sea, before the asteroid that ended the age of the dinosaurs. That helps explain how freshwater fish communities recovered after the extinction, and it helps scientists identify the many isolated fossil bones found across North America.

Conclusion

Two tiny fish, a few centimetres long and hidden in black rock for 66 million years, have redrawn part of the fish family tree. Using synchrotron light, researchers in Alberta found that a relative of the deep-sea beardfish once swam in fresh water, and that the percomorphs — the group that includes perch, bass and mackerel — were already in Cretaceous rivers. The ancestors of the fish we know today were already there before the asteroid fell. It is a small discovery with a long reach: proof that the biggest stories in evolution are sometimes written in the smallest fossils.

This article is for general information and education only. It is not legal or financial advice.

Sources

Faizan Altaf

Faizan Altaf is the founder and author of findivoza.com, a news blog covering world, Pakistan, business, technology, health and sport in plain English. He writes for general readers who want clear, trustworthy news without jargon. His work focuses on explaining what happened, why it matters, and what to watch next.

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