Most people picture the time of dinosaurs as a steamy, tropical world. But during the Late Cretaceous period, northern Alaska was a different kind of wild. Located far above the Arctic Circle, it endured months of winter darkness and freezing temperatures – even as much of the planet remained warm. Think sub-Arctic Canada today: cold, wet and seasonal.
A diverse, international team of scientists has now uncovered a remarkable discovery: the world’s oldest known relatives of salmon and carp lived in this extreme environment.
Using the latest in 3D imaging technology, Lisa Van Loon and Neil Banerjee from Western and their collaborators analyzed fossilized fish bones found in the rocks of the Prince Creek Formation in Alaska to reveal a previously undiscovered polar ecosystem. The findings were published May 7 in the journal Papers in Paleontology.
“The synchrotron allowed us to virtually reconstruct these fish in 3D, bone by bone. It’s an incredible example of how modern imaging tools are unlocking secrets from the deep past.”— Lisa Van Loon, adjunct research professor, Western
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“These discoveries suggest this remote region may have been an evolutionary launchpad for fish that now dominate northern rivers and lakes worldwide,” said Van Loon, adjunct research professor in the departments of Earth sciences and anthropology at Western.
Some of the fossils discovered in Alaska were barely larger than a pin head and were deeply embedded in rock. Traditional fossil preparation, which involves carefully removing surrounding sediment by hand, wasn’t an option; the specimens were simply too fragile.
Using synchrotron micro-computed tomography (micro-CT) scanning technology at the Advanced Proton Source, with support from the Canadian Light Source, researchers scanned the fossil-bearing rocks without physically disturbing them. The ultra-bright, high-resolution X-ray beams allowed them to digitally reconstruct the anatomy of these ancient fish in 3D, revealing intricate structures such as jaws, teeth and fin rays in remarkable detail.
“Many of these fossils were so delicate and deeply encased in rock that traditional preparation would have destroyed them,” said Banerjee, an Earth sciences professor at Western. “Using synchrotron micro-CT scanning, we were able to peer inside the rock in extraordinary detail – resolving tiny jaw bones and teeth without laying a chisel on them. This technology has completely transformed how we study ancient life.”
The scans made it possible to identify entirely new species, some of which represent the earliest-known members of fish groups that today dominate northern rivers and lakes, such as salmon, carp and pike.
Sivulliusalmo alaskensis, meaning “first salmon of Alaska” in Iñupiaq, is now the earliest known member of the salmon family, eclipsing previous records by nearly 10 million years. The earliest known cypriniform, part of the same group as today’s minnows and carp, was also found, marking its first appearance in North America (as they were previously only found in Asia and Europe).
Newly found species of pike-like fish also lived at Prince Creek Formation, some 73 million years ago, including Archaeosiilik gilmulli and Nunikuluk gracilis, as they successfully adapted to the Arctic’s long winters. Sharks like Squatina (a relative of angel sharks), sturgeon and paddlefish, were also revealed within the fossil samples.
“The synchrotron allowed us to virtually reconstruct these fish in 3D, bone by bone,” said Van Loon. “It’s an incredible example of how modern imaging tools are unlocking secrets from the deep past.”
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