Oncorhynchus rastrosus was the largest species of salmon to ever exist on Earth, but its tusk-like teeth are what really set it apart from its modern cousins.
Claeson et al.Fossilized remains of Oncorhynchus rastrosus next to artistic renditions of the prehistoric fish.
Between 5 and 12 million years ago, an ancient salmon species with warthog-like tusks swam up and down the coastline of the Pacific Northwest. Its name was Oncorhynchus rastrosus.
Measuring upwards of eight feet in length and more than 400 pounds, O. rastrosus was a formidable fish. It likely used its “fearsome” teeth to fiercely defend itself and its young against predators.
The prehistoric salmon has been extinct for over 4.5 million years, but researchers have only recently discovered the truth about its unique features.
Discovering ‘Oncorhynchus Rastrosus’
Fossils of O. rastrosus were first discovered near Gateway, Oregon, in the 1970s. Because the creature’s teeth had separated from the rest of its body, researchers were unable to confirm how they were positioned in the fish’s mouth. They initially believed that the fangs pointed downward, similar to a saber-toothed tiger.
Other modern Pacific salmon species have teeth that point down, so the team inferred that O. rastrosus likely did, too. They gave O. rastrosus the nickname “saber-toothed salmon.”
However, in 2014, scientists found a complete fossilized skull in Gateway that showed that the fish’s teeth instead pointed outwards, like a warthog.
At first, the research team believed it was a deformity of that specific specimen, but CT scans revealed features of the upper jaw bone that proved that the creature’s teeth were meant to point outward.
“As a result, the species should be renamed the ‘spike-toothed salmon,'” Professor Kerin Claeson of the Philadelphia College of Osteopathic Medicine stated in her study of the creature, which was just published in the journal PLOS One.
With the ancient salmon’s skeletal structure confirmed, researchers then turned to determining exactly what it used its bizarre tusks for.
The Largest — And Strangest — Prehistoric Salmon
University of OregonA “spike-toothed salmon” fossil.
Oncorhynchus rastrosus is the largest known salmon to ever exist on Earth. The fish measured between 7.9 and 8.9 feet in length and weighed over 400 pounds, and its teeth were more than an inch long.
Unlike other species of salmon, O. rastrosus probably didn’t use its unique teeth to hunt.
“While it’s unclear exactly what these teeth may have been used for, we believe they were likely used for fighting — either against other spiked-toothed salmon or as a defense against predators — or as a tool for digging out nests,” stated Claeson, according to SciNews.
“But the teeth likely weren’t used for catching prey, since Oncorhynchus rastrosus is believed to have been a filter-feeder that dined on plankton,” Claeson continued.
Both males and females of the species possessed the teeth, and scientists stated that both sexes were “equally fearsome.”
“We have known for decades that these extinct salmon from Central Oregon were the largest to ever live,” said Claeson. “Discoveries like ours show they probably weren’t gentle giants.”
After reading about the tusk-like teeth of Oncorhynchus rastrosus, dive into the story of the candiru, the Amazonian fish that reportedly swims up human penises. Then, read about 29 more fascinating animals from around the world.
