Smilodonichthys Rastrosus: A New Pliocene Salmonid Fish from Western United States

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Date

1972-03

Authors

Cavender, Ted M.
Miller, Robert Rush

Journal Title

Journal ISSN

Volume Title

Publisher

Museum of Natural History, University of Oregon

Abstract

In western North America, the family Salmonidae is comprised of a diverse number of species (upwards of 30) belonging to seven genera assigned to three subfamilies (Norden, 1961). Though more than half of these species are endemic to the area, an astonishingly few fossil specimens have been discovered which can help document the evolution that has taken place in this group. An exception is the one described in this paper which adds importantly to our understanding of the past life of these fishes. Materials of this fossil salmonid were collected over a period of fifty years from Pliocene, Pacific-slope localities in California and Oregon. As early as 1917, vertebrae, teeth and skull fragments of an extremely large but unfamiliar type of fish were unearthed, along with mammalian remains, at Pinole, Contra Costa County, California. Only within recent years, however, has it been possible to identify these with certainty as being the remains of an extinct form of salmonid that once was distributed in the coastal regions of the Pacific Northwest, probably much the way that Pacific salmon (Oncorhynchus) are today. In 1950 and again in 1964, more complete specimens were discovered of this unusual species from a Pliocene gravel pit in northcentral Oregon. The last find consisted of a large skull which is outstanding for its completeness and detail of preservation. It is a description of this skull that forms the main context of the present paper and which has allowed fruitful comparison to be made with living salmonids. The name Smilodonichthys rastrosus is proposed for this previously undescribed species. Because of its high degree of morphological distinction from other members of the Salmonidae, this species is made the type of a new genus. A number of its osteological features indicate a phyletic relationship closest to Oncorhynchus, yet none of the extant species of that genus approaches the fossil in the specialization of its feeding mechanism.

Description

52 pages

Keywords

Oncorhynchus, Salmonidae, Pacific-slope, Smilodonichthys rastrosus

Citation