Giant prehistoric salmon had fearsome, tusk-like teeth

A team of researchers led by the Philadelphia College of Osteopathic Medicine (PCOM) has recently described a remarkable species of salmon, known as Oncorhynchus rastrosus, which lived in the North American Pacific Northwest millions of years ago and boasted an unusual pair of protruding front teeth resembling tusks.

“In the Pacific Northwest, Oncorhynchus is the most celebrated and species-rich salmonine subclade, yet the twelve living species represent only a portion of their clade’s historical diversity,” wrote the study authors. 

Spike-toothed salmon

Previously, researchers believed that the large front teeth of O. rastrosus, which earned it the nickname “saber-toothed salmon,” pointed backward into its mouth. 

However, recent CT scans and thorough analyses of various fossils have found that these teeth extended sideways out of the mouth, akin to the tusks of a warthog. Based on these findings, the researchers suggested renaming the species to “spike-toothed salmon.”

Purpose of tusk-like salmon teeth 

While the actual function of these distinctive teeth remains a matter of debate, the researchers argued that they could have been used for combat with other members of their species or for defense against predators. 

Another possibility is that the teeth served a practical purpose in nest-building during the spawning season. It is unlikely that the teeth were used for capturing prey, as O. rastrosus is believed to have been a filter-feeder, primarily consuming plankton.

“The discoveries like ours show they probably weren’t gentle giants,” said lead author Kerin Claeson, a paleontologist at the PCOM. “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.”

Both males and females had protruding teeth

Senior author Edward Davis, an associate professor of Earth Sciences at the University of Oregon and director of the Condon Collection at the UO’s Museum of Natural and Cultural History, expressed enthusiasm about the new insights: “I’m delighted that we have been able to put a new face on the giant spike-toothed salmon, bringing knowledge from the field in Oregon to the world.”

“We also stress that females and males alike possessed enormous, tusk-like teeth. Therefore, the sexes were equally fearsome,” added co-author Brian Sidlauskas, an expert in ichthyology Oregon State University. This feature highlights the potentially aggressive and competitive nature of both male and female spike-toothed salmon.

“Because male and females possess hypertrophied premaxillae and lateral premaxillary spikes, the former common name “Sabertoothed Salmon” no longer reflects our understanding of the species’ morphology. Accordingly, we redub O. rastrosus the Spike-Toothed Salmon and postulate that its spikes were multifunctional, serving as defense against predators, in agonism against conspecifics, and as a practical aid to nest construction,” the authors concluded.

More about salmon teeth

Salmon have a set of teeth that are well-adapted to their diet and lifestyle, primarily suited for grabbing and holding onto prey. These teeth are small but sharp, lining the jaws, and in some species, they can also be found on the roof of the mouth. 

Function of salmon teeth

The primary function of these teeth is not for chewing but for ensnaring slippery prey like fish and insects, which is crucial since salmon are predominantly carnivorous.

Structure

Interestingly, the structure and robustness of salmon teeth can vary among species and even change throughout the life stages of the fish. For example, when young salmon (smolts) transition from freshwater to the ocean, their diet changes, and this can be reflected in the development of their teeth to better suit their new food sources.

Spawning

Additionally, during the spawning phase, some male salmon develop what’s called a “kype,” which is a pronounced curvature of the jaws and teeth. This feature helps them in fights for dominance and the right to mate. 

Overall, the teeth of salmon are integral to their survival and reproductive strategies, emphasizing their role as effective predators within their aquatic environments.

The study is published in the journal PLoS ONE.

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