Long before humans cast lines into icy rivers, ancient salmon swam through prehistoric Arctic waters — 73 million years ago. Now, a newly identified fossil species pushes the origins of this iconic fish family 20 million years further into the past.
Key Points at a Glance
- Discovery of Sivulliusalmo alaskensis, the earliest known ancestor of modern salmon
- Fossils date back 73 million years, placing salmonids in the Cretaceous Arctic
- Salmonids thrived in extreme seasonal environments, much like today
- Research highlights Alaska as a cradle of northern fish evolution
In the icy shadows of the dinosaurs, a different kind of survivor swam silently through prehistoric Arctic rivers — a fish whose descendants would one day battle upstream in the heart of the Pacific Northwest. Scientists have uncovered fossil evidence of a previously unknown species of ancient salmonid in Alaska’s Prince Creek Formation, and it’s making waves in evolutionary biology. The newly named Sivulliusalmo alaskensis isn’t just another fossil — it’s now the oldest known member of the salmon family.
Published in Papers in Palaeontology, the discovery adds an astounding 20 million years to the known history of salmonids. It shifts their evolutionary origin story not only further back in time but also firmly into northern, polar regions. “This is not only a new species; it’s the oldest salmonid in the fossil record,” said Patrick Druckenmiller, director of the University of Alaska Museum of the North and senior author on the study.
The genus name Sivulliusalmo — derived from the Inupiaq word sivulliuqti meaning “first” — reflects the species’ pioneering place in salmon evolution. The fossil remains, painstakingly extracted from buckets of gravel and sand and analyzed using micro-CT scanning, consist mainly of tiny jaws and teeth, some no larger than a pencil eraser. But these diminutive remnants hold enormous significance.
While dinosaurs prowled the land, Arctic rivers in the Late Cretaceous — about 73 million years ago — flowed with ancestors of today’s salmon, pike, grayling, and even members of the carp family. “Many of the fish groups that we think of as being distinctive today in the high-latitude environment in Alaska were already in place at the same time as dinosaurs,” Druckenmiller noted.
The presence of salmonids during this warm Cretaceous period is especially remarkable. Despite globally higher temperatures, the Arctic still experienced stark seasonal changes in light and temperature. These conditions, it turns out, were ideal training grounds for the kind of resilience we now associate with salmon. Andrés López, curator of fish at the UA Museum and a co-author on the paper, explains: “Salmon were already the kind of fish that do well in a place where those dramatic shifts were happening.”
It’s a trait that modern salmon have inherited — the ability to navigate environments marked by fluctuation and adversity. And now, it appears that these evolutionary roots run deeper and colder than anyone previously suspected.
This discovery didn’t happen overnight. For more than a decade, paleontologists at UAF have been analyzing countless microfossils from the Colville River sites, a region already renowned for its dinosaur bones. But fish fossils, though plentiful, are often ignored due to their fragmentary nature and tiny size. “These types of fossils are often overlooked,” said Druckenmiller. “You couldn’t begin to understand a modern Arctic ecosystem without understanding the smallest animals that live there. The same is true for ancient ecosystems.”
The research effort involved a collaboration of institutions across North America, including scientists from Western University, the University of Colorado Boulder, Princeton, and Florida State University. By combining expertise in fish taxonomy, paleoenvironments, and advanced imaging, the team was able to reconstruct detailed views of jaws and bones — and make a compelling case for the Northern origin of salmonids.
The implications ripple far beyond taxonomy. The study reinforces the idea that high-latitude environments were evolutionary crucibles — not peripheral zones. As Druckenmiller puts it, “Northern high latitude regions were probably the crucible of their evolutionary history.”
In a time when climate change is reshaping Arctic ecosystems at unprecedented speed, understanding their ancient resilience offers valuable perspective. Salmon, it seems, have always been creatures of extremes — forged in ice and flood, thriving where others failed, and leaving behind a legacy written not just in DNA, but in stone.
Source: University of Alaska Fairbanks
