Oncorhynchus rastrosus
a.k.a Sabre-toothed Salmon.

Name: Oncorhynchus rastrosus.
Phonetic: On-ko-rin-kus ras-tro-sus.
Synonyms: Smilodonichthys rastrosus.
Classification: Chordata,‭ ‬Teleostomi,‭ ‬Actinopterygii,‭ ‬Salmoniformes,‭ ‬Salmonidae.
Species: O.‭ ‬rastrosus.
Diet: Planktonic filter feeder.
Size: Up to‭ ‬2.7‭ ‬meters long.
Known locations: Pacific coastlines of North America,‭ ‬particularly California and Oregon.
Time period: Late Miocene through to the Pleistocene.
Fossil representation: Many specimens.

       Oncorhynchus rastrosus is a prehistoric species of salmon and one known to have grown to very large sizes.‭ ‬Oncorhynchus rastrosus is more commonly known as the sabre-toothed salmon,‭ ‬a name the species got from a pair of greatly enlarged teeth that grew down from the upper jaw of males,‭ ‬and may have been most developed when getting ready to spawn.‭ ‬These teeth are thought to have been used by males to compete against one another in much the same way that their smaller relatives do today.‭ ‬Despite this fearsome appearance however,‭ ‬Oncorhynchus rastrosus is thought to have mostly been a filter feeder based upon the observation that the gill rakers are both more numerous and more finely built than most modern forms which are more predatory in their diets‭ (‬though the sockeye salmon,‭ ‬Oncorhynchus nerka,‭ ‬is also known to be a planktonic feeder when adult‭)‬.‭ ‬Exceptionally high levels of plankton have also been recorded in Miocene aged marine deposits,‭ ‬which reveals that Oncorhynchus rastrosus probably grew so big as a result of both a greater abundance of food,‭ ‬as well as a slower lifestyle which would not require calories for fast pursuit swimming,‭ ‬meaning that more could go to growth.

Further reading
-‭ ‬Smilodonichthys rastrosus:‭ ‬A new Pliocene salmonid fish from Western United States.‭ ‬-‭ ‬Museum of Natural History,‭ ‬University of Oregon.‭ ‬-‭ ‬Ted M.‭ ‬Cavender‭ & ‬Robert Rush Miller‭ ‬-‭ ‬1972.
-‭ ‬Miocene salmon‭ (‬Oncorhynchus‭) ‬from Western North America:‭ ‬Gill Raker evolution correlated with plankton productivity in the Eastern Pacific.‭ ‬-‭ ‬Palaeogeography,‭ ‬Palaeoclimatology,‭ ‬Palaeoecology vol‭ ‬249,‭ ‬Issues‭ ‬3-4‭ ‬p‭ ‬412-424‭ ‬-‭ ‬Thomas P.‭ ‬Eiting‭ & ‬Gerald R.‭ ‬Smith‭ ‬-‭ ‬2007.



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