‘Saber-toothed salmon’ was more of a water warthog, study finds

(CN) — At 8.9 feet long, Oncorhynchus rastrosus was the largest salmon to ever swim the seas, but another claim to fame gave rise to its fearsome moniker: Surviving fossils showed evidence of two large front teeth, gaining it the nickname “saber-toothed salmon.” Researchers now say the truth may be slightly less edgy.

Full teeth weren’t attached to the salmon fossils, but scientists widely believed the fish had downward-pointing fangs, similar to the iconic saber-toothed tiger that once roamed the American wilderness. But newer fossils convinced researchers the saber-toothed salmon's teeth were more akin to a warthog’s tusks than the prehistoric cat’s fangs, according to research published Wednesday in the open-access journal PLOS 1.

Paleoichthyologist Kerin Claeson of the Philadelphia College of Osteopathic Medicine and her team reexamined the standard image of the salmon after running CT scans on fossils collected over various years. They concluded that the salmon's teeth must have protruded out to the sides of its mouth.

Researchers suggest that the public adopt the more accurate name “spike-toothed salmon” for the species instead.

According to Claeson, this new understanding of the spike-toothed salmon’s physiology offers fresh insight into how these prehistoric fish behaved.

“Discoveries like ours show they probably weren't gentle giants,” 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."

Co-author Brian Sidlauskas, professor and curator of fishes at Oregon State University, said all the fish displayed the signature teeth.

“We also stress that females and males alike possessed the enormous, tusk-like teeth. Therefore, the sexes were equally fearsome,” he said.

Since females also sported the tusk-like teeth, they were likely used to defend against predators, the authors said. Freshwater fossils showed larger teeth than marine specimens, suggesting that the spike-toothed salmon’s teeth grew larger as they migrated upstream to reproduce.

Whatever the teeth were used for, the spike-toothed salmon almost certainly didn’t hunt with them. Unlike many species, such as the Atlantic salmon, the spike-toothed salmon only ate plankton, researchers believe. The salmon had lots of long, skinny gill rakers — structures made for filtering out particles and tiny prey as water passes through the fish’s gills. Modern sockeye salmon, which feed almost entirely on plankton, have similar rakers.

The spike-toothed salmon also lacked the bite apparatus of modern predatory salmon and had a proportionally smaller head. However, the spike-toothed salmon’s mouth was much smaller than most suspension feeders, leading the researchers to believe that it fed differently than other plankton eaters, which generally charge forward into clouds of the tiny sea creatures.

Researchers confirmed that the fish traveled from saltwater to freshwater to spawn, and they discovered that males and females of the species had noticeable differences in their skull and fin shapes.

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