The largest salmon species ever discovered, Oncorhynchus rastrosus, possessed tusk-like teeth that served multiple purposes such as competing with rivals, defending itself from predators, and digging nests. This prehistoric salmon lived 5 million years ago, measuring up to 2.7 meters in length and weighing over 180 kg. Oncorhynchus rastrosus was found in the northwestern seas of North America during the Mesozoic era, surpassing modern-day Chinook salmon in size and weight.
Initially described in 1972, O. rastrosus was thought to have backward-growing fangs, earning it the nickname “sabre-toothed salmon” due to its distinctive pair of teeth. However, recent studies using computed tomography revealed that these 5 cm long curved teeth resemble tusks of warty pigs. The purpose of these unique tusks remains unclear, though researchers believe they were used for combat, protection, nest digging, or aiding in swimming upstream.
While O. rastrosus likely did not use its teeth for hunting, they may have functioned as water filters to feed on plankton, similar to other filter-feeding aquatic species. This specialized feeding mechanism, along with their large gill rakers, enabled them to grow to enormous sizes by efficiently consuming nutrients from the water. Living in warm environments with abundant water and food sources, O. rastrosus eventually went extinct as the Earth cooled, impacting their resources and survival.
Moving forward, scientists plan to conduct further analyses on O. rastrosus specimens to better understand the role and evolution of their tusks. Despite their extinction, these giant salmon provide valuable insights into prehistoric aquatic ecosystems and the adaptive strategies of ancient marine species.