These Massive, Extinct Salmon Had Spiky Teeth Like a Warthog’s Tusks

Between 5 million and 12 million years ago, enormous salmon swam through the waters of what is now the Pacific Northwest. Weighing up to 400 pounds and measuring more than eight feet long, these hulking creatures—the largest salmon that ever lived—had a pair of long, curved teeth protruding from the top jaw.

For decades, scientists thought these two-inch-long chompers pointed downward—similar to those of a saber-toothed cat. However, a new analysis is painting a different picture: Now, scientists believe the teeth jutted out sideways, like a warthog’s tusks.

They described their findings Wednesday in the journal PLOS One.

Called Oncorhynchus rastrosus, the extinct species was first described from fossils in 1972. But in these preserved remains, the upper jaw bones and long teeth were separated from the rest of the skull. Scientists inferred the teeth had pointed down, so they nicknamed the creatures “saber-toothed salmon.”

“It was just natural to assume that when you put this [tooth] back into place, that’s the arrangement that it’s going to be,” says study co-author Kerin Claeson, a paleoecologist at Philadelphia College of Osteopathic Medicine, to Live Science’s Caroline Tien.

But in 2014, scientists discovered new O. rastrosus fossils in Oregon—with the jaw and teeth still attached, giving paleontologists a much clearer look at their orientation. Researchers also decided to revisit older fossils, using new technologies, including CT scans, to give them a second look. Now, they’ve given O. rastrosus a brand-new nickname: “spike-toothed salmon.”

The newer fossils revealed that both male and female members of the species had the spikes, which likely started growing as they matured into adulthood.

“This is all part of the scientific process,” says study co-author Edward Davis, a paleobiologist at the University of Oregon, to Popular Science’s Laura Baisas. “You have an idea, and you get new information. It’s a good reminder of the humility you need to have as a scientist.”

“The new reconstruction is supported by very convincing evidence,” says Mark Wilson, a paleontologist at the University of Alberta in Canada who was not involved with the study, to National Geographic’s Riley Black.

But while scientists have solved one big mystery about the giant fish, they still have lots of questions. Chief among them: Why did the salmon evolve to have such long spikes on their heads? And what did they use these odd teeth for?

One theory is that the fish used the spikes to defend themselves against competitors or predators—or, at least for males, to give off the appearance of being tough and scary. The defense hypothesis makes sense in the context of how fish move through the water—by flexing their bodies side to side. The salmon could’ve easily used these same, strong muscles to swing the spikes against rivals.

“Imagine a one-pound geology hammer, sharpened and wielded by 200 pounds of lateral muscle,” says Claeson to National Geographic.

This idea also makes sense given the large size of O. rastrosus, which would’ve made the species a target for hungry carnivores. One 400-pound fish, after all, is “a lot of meat,” Claeson tells Live Science.

“Discoveries like ours show they probably weren’t gentle giants,” she says in a statement.

Another possibility is that the salmon used their spiky teeth to dig nests in riverbeds, or to latch onto something for a quick rest break while swimming upstream—“sort of like if you’re holding on to the side of the swimming pool,” Davis tells Popular Science.

Researchers have mostly ruled out the idea that the salmon used their spikes to catch and kill prey. They believe this because O. rastrosus had lots of “gill rakers,” or bony protuberances that modern fish use to filter plankton out of the water for food. The extinct salmon’s massive size also supports this idea, since many of today’s largest living fish—including the whale shark—are also filter feeders that subsist on plankton.

No matter how the species used its large teeth, O. rastrosus could offer a window into the past—and, possibly, the future. The enormous salmon lived during the Miocene and Pliocene epochs, when Earth was much warmer, and went extinct as the planet began to cool off. As global temperatures rise once again, O. rastrosus might give scientists some clues about what to expect amid the changing climate.

“By looking at how the giant salmon lived on this much warmer Earth, we can think about what resources are going to change over the next 80 years if our Earth is returning to that warmer state,” Davis tells Popular Science.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.