The sabertooth salmon (Oncorhynchus rastrosus), a giant species of salmon that swam in Pacific Northwest waters from the mid-Miocene to early Pliocene, fought with tusk-shaped teeth during the spawning season, according to a research team led by California State University paleontologist Dr. Julia Sankey.
Oncorhynchus rastrosus in Proto-Tuolumne River. Image credit: Jacob Biewer.
Oncorhynchus rastrosus, also known as giant, tusk-toothed salmon, lived along the Pacific coast of North America (California, Oregon, and Washington) roughly 11 to 5 million years ago.
This ancient fish was large, approximately 3-9 feet (1-3 m) long and nearly 400 pounds (177 kg) in weight, much larger than the typical salmon found in the Pacific today.
The species migrated from the Pacific Ocean to inland rivers to spawn, as salmon do today. And it was planktivorous, based on numerous gill-rakers, and a few, small teeth.
Oncorhynchus rastrosus also had two, large (0.8-1.2 inches, or 2-3 cm, long), upper tusk-shaped teeth.
“A great deal is known about Oncorhynchus rastrosus from previous studies. However, there are still gaps in our knowledge about this fascinating giant salmon,” Dr. Sankey and co-authors said.
To see if the tusk-shaped teeth played an important role in breeding of this species, the researchers compared 51 different fossils from ancient deposits of both freshwater and saltwater environments.
“Teeth from freshwater deposits are not only larger, but they are also more recurved, and the tooth tips more worn and blunt. In addition, their bony tooth bases are considerably larger,” they said.
“Teeth from coastal marine deposits are smaller, straighter, their tooth tips sharper, and their tooth bases smaller.”
“This supports our hypothesis that Oncorhynchus rastrosus did developmentally change between the marine and freshwater stages of their lives, as modern salmon do today.”
The paleontologists think it is likely Oncorhynchus rastrosus were using their tusk-shaped teeth for fighting and display against each other during the spawning season, up in the ancient rivers of California.
“These giant, spike-toothed salmon were amazing fish. You can picture them getting scooped out of the Proto-Tuolumne River — near Modesto, California — by large bears 5 million years ago,” Dr. Sankey said.
Dr. Sankey and co-authors presented their research October 27 in Salt Lake City, Utah, at the 76th Annual Meeting of the Society of Vertebrate Paleontology.
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Julia T. Sankey et al. Did the giant, tusk-toothed salmon (Oncorhynchus rastrosus) morph before migration upriver like modern salmon do today? Abstracts of the 76th Annual Meeting of the Society of Vertebrate Paleontology, p. 217-218
