Extinct Spike-Toothed Salmon Used Tusks for Competition and Nest-Building, Study Finds

Oncorhynchus rastrosus, an extinct species of giant salmon that lived in the North American Pacific Northwest a few million years ago, had a pair of front teeth that projected out from the sides of its mouth like tusks, according to a new study published in PLOS ONE.

The fish, which could reach up to 8.9 feet in length, was initially thought to be a 'sabre-toothed salmon' due to the backwards-pointing orientation of its front teeth, but recent analysis suggests the teeth pointed sideways out of the fish's mouth, similar to a warthog.

Researchers believe the salmon used the tusks for defense against predators, competition with other salmon, and to construct nests for their eggs. Both males and females had the distinctive tusk-like teeth, indicating they were used for purposes other than hunting. The study provides a new reconstruction of the fish's face, showing that its impressive teeth stuck out sideways from its snout, rather than curving downward as previously thought.

Why this matters: The study sheds new light on the behavior and physiology of this extinct giant salmon species, providing insights into the ecological dynamics of ancient marine environments. The findings emphasize the importance of continually reevaluating scientific assumptions and open new avenues for understanding the evolution and adaptations of extinct species.

The study also revealed that the fish had a side-to-side swimming motion, with their strongest muscles devoted to these movements, which would have allowed them to take strong swings against predators or rivals. "The teeth were likely used for scraping and moving sediment to construct nests, as well as for defending those nests from other fish," the researchers noted.

O. rastrosus was the largest salmon in the Oncorhynchus genus and inhabited the North Pacific coasts of Japan and North America before going extinct around 5 million years ago. The species fed on plankton and had a smaller mouth compared to other plankton-eating fish, indicating they had a unique feeding mechanism.

The authors suggest the species should be renamed the 'spike-toothed salmon' to reflect the accurate configuration of its teeth. The study provides a fascinating glimpse into the life and adaptations of this ancient giant salmon, highlighting the importance of ongoing paleontological research in understanding the diversity and evolution of extinct species.

Key Takeaways

• Extinct giant salmon Oncorhynchus rastrosus had tusk-like sideways-pointing teeth.
• Teeth used for defense, competition, and nest construction, not hunting.
• Largest salmon in Oncorhynchus genus, up to 8.9 feet long, extinct ~5 mya.
• Swam side-to-side, with strong muscles for this motion to defend nests.
• Should be renamed 'spike-toothed salmon' to reflect accurate tooth configuration.