Fossil Polypores from Idaho

Abstract

In June, 1946, we spent a day searching for fossil plant remains in the late Tertiary deposits in southwestern Idaho. Our primary quest in this region was for petrified evergreen cones that have occasionally turned up, although only in such quantity as to whet the appetite of collectors. The focal point of that day's collecting was approximately 10.5 miles south of Bruneau and .5 mile east of state highway No. 51 which runs-south Mountain Home, Idaho, through Owyhee County into Nevada. In the course of the day one member of our party, Mr. J. M. Dodds, a County Commissioner, of Boise, discovered a fine specimen of a petrified polypore. More recently, Mr. S. H. Osgood, of Rupert, Idaho, has sent us a fragment of another specimen. Although both of our specimens seem to be clearly referable to -the fossil Fomes idahoensis Brown (Brown, '40), in view of the great rarity of fossil polypores a brief record of the specimens seems worth while. This part of Idaho is well known to local mineral collectors for its abundance of fossil wood, as well as the occasional cones. Most of these fossils are weathering out of a loosely consolidated, fine white sandstone which is overlain by a brownishbuff sandstone of a harder texture likewise yielding petrified plan't remains. Overlying the productive plant beds is a horizon which yields an abundance of wellpreserved, fish jaws (Mylocybrinus robustus Leidy). The only stratigraphical study of the beds in this region is that of Piper's ('24), and the horizon which our fossils were obtained was apparently in his group No. 8 which is described as Lake sediments, semi-consolidated, white, gray, and buff sandstones and sandy shales, volcanic ash; .... These beds have been considered to be of Pliocene age although it is possible that they may be of later origin. In a recent letter (February 20, 1947) Dr. Bobb Schaeffer has informed us of a collection of Mylocyprinus robustus fossil fish pharyngeals in the American Museum that were collected from an area in southwest Idaho between 'Catherine and Sinker Creeks.' This particular locality is considered to be Pleistocene and as this genus has not previously been reported older formations I am wondering if your horizon might not also be referable to that period.