Ancient Salmon and Pike Ancestors Thrived in Alaska’s Freshwater 73 Million Years Ago

Paleontologists have identified three new fossil species. Sivulliusalmo Alaskensis was found in a purine cream formation in northern Alaska, USA.

“Sivulliusalmo Alaskensis reveals significant insights,” remarked Dr. Patrick Druckenmiller, the director of the University of Alaska Museum in the North.

“Our research uncovers several additional species of ancient fish new to the Arctic, including two new pike species: Archaeosiilik Gilmulli and Nunikuluk Gracilis, as well as the oldest record within the group comprising carp and minnows.”

“Many fish we now consider unique to Alaska’s high-latitude environment existed alongside dinosaurs.”

The discovery of Sivulliusalmo Alaskensis adds an impressive 20 million years to the fossil history of the salmon family.

Previously, the oldest known salmonidae fossil was from British Columbia and Washington.

“It’s noteworthy that the Salmonidae, which typically thrives in cold water, adapted and flourished during the warm Cretaceous period, enduring for millions of years amidst significant geographical and climatic changes,” noted Andres Lopez, Fish Curator at the University of Alaska in the north.

“Even though the Arctic was warm during that era, there would still be substantial seasonal variations in temperature and sunlight, much like today.”

“Salmon were among the fish adept at navigating these dramatic shifts.”

“Despite the planet’s numerous geological and climatic transformations, the ancestors of the same species group persisted in dominating the region’s freshwater ecosystems.”

The new species is the latest finding from the Prin Creek Formation, renowned for its dinosaur fossils discovered along the Colville River in northern Alaska.

During the Cretaceous period, Alaska was significantly closer to the Arctic than it is today.

“Fish fossils are among the most abundant in the Purine Creek Formation, yet they are challenging to distinguish in the field,” stated Dr. Druckenmiller.

“Consequently, we transported the fine sand and gravel samples to our museum lab, where microscopic analysis revealed the bones and teeth.”

“Our new findings heavily rely on small, fossilized jaws, some of which are small enough to fit on the edge of a pencil eraser.”

For detailed examination, the researchers employed micro-computed tomography to digitally reconstruct the small jaws, teeth, and other bones.

“We identified very distinct jaws and other components of the salmon family, which were recognized as belonging to this lineage,” said Dr. Druckenmiller.

“The presence of salmonidae in the Cretaceous polar regions and their coexistence with common low-light fish from this period suggests that salmonidae likely thrived in northern climates.”

“The high latitudes of the northern regions may have been vibrant centers for their evolutionary development.”

This paper was published in the journal Paleontology papers.

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Donald B. Brinkman et al. 2025. Fish from the Purine Cream Formation in the northern slopes of Alaska: the pre-Cretaceous and their paleobiogeographic significance. Paleontology papers 11(3): E70014; doi: 10.1002/spp2.70014