An extinct species of giant salmon called Oncorhynchus rastrosus sported a pair of front teeth that projected out from the sides of its mouth like tusks, according to new research.
Oncorhynchus rastrosus: (A) CT model of holotype; (B) holotype in anterior view of skull, prior to complete preparation and CT scan; (C) artist’s rendering skull of male iconic fish with accurate spike-tooth configuration; (D) artist’s rendering of complete female iconic fish with accurate spike-tooth configuration. Scale bar blocks – 1 cm each. Image credit: Claeson et al., doi: 10.1371/journal.pone.0300252.
Oncorhynchus rastrosus lived along the Pacific coast of North America (California, Oregon, and Washington) roughly 11 to 5 million years ago.
The extinct species was first described from fossils found at the freshwater Gateway Locality of the Madras Formation, near the town of Gateway, Jefferson County, Oregon, in the 1970s.
The fish reached between 2.4 and 2.7 m (7.9-8.9 feet) in length and nearly 177 kg (400 pounds) in weight by some estimates, making it the largest known member of the family Salmonidae ever to live.
The species migrated from the Pacific Ocean to inland rivers to spawn, as salmon do today. And it was planktivorous, based on numerous gill-rakers, and a few, small teeth.
But Oncorhynchus rastrosus also had two 2-3-cm- (0.8-1.2-inch-) long upper teeth.
Initially, paleontologists thought these oversized teeth pointed backward into the mouth like fangs, in large part because fossils of the teeth were found apart from the rest of the skull. This led to the common name ‘saber-toothed salmon.’
But through the new CT scans and analysis of various Oncorhynchus rastrosus fossils collected over the years, Philadelphia College of Osteopathic Medicine’s Professor Kerin Claeson and her colleagues have now been able to confirm that the teeth actually pointed sideways out of the fish’s mouth, similar to a warthog.
“As a result, the species should be renamed the ‘spike-toothed salmon’,” the paleontologists said.
“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.”
“It’s also possible the teeth were used for multiple purposes,” they added.
“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.”
“We have known for decades that these extinct salmon from Central Oregon were the largest to ever live. Discoveries like ours show they probably weren’t gentle giants,” Professor Claeson said.
“These massive spikes at the tip of their snouts would have been useful to defend against predators, compete against other salmon, and ultimately build the nests where they would incubate their eggs.”
“I’m delighted that we have been able to put a new face on the giant spike-tooth salmon, bringing knowledge from the field in Oregon to the world,” said Dr. Edward Davis, a researcher at the University of Oregon and director of Condon Collection at the University of Oregon’s Museum of Natural and Cultural History.
“We also stress that females and males alike possessed the enormous, tusk-like teeth. Therefore, the sexes were equally fearsome,” said Professor Brian Sidlauskas, curator of fishes at Oregon State University.
The team’s results were published in the journal PLoS ONE.
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K.M. Claeson et al. 2024. From sabers to spikes: A newfangled reconstruction of the ancient, giant, sexually dimorphic Pacific salmon, Oncorhynchus rastrosus (SALMONINAE: SALMONINI). PLoS ONE 19 (4): e0300252; doi: 10.1371/journal.pone.0300252