. Bulletin. Natural history; Natuurlijke historie. COROSAURUS ALCOVENSIS. Fig. 2. Simplified geologic map of Casper-Goose Egg-Freeland Junction area, Natrona County, Wyoming, after Fig. 1. Triassic and undiflTerentiated Permo-Triassic sediments stippled. Areas of Quaternary surficial deposits marked by dashed outlines. Faults indicated by heavy lines. G= Cam- brian; J = Jurassic; K = Cretaceous; K/J = undiflTerentiated Cretaceous and Jurassic; P = Permian; pG = Precambrian; P/C = undiflTerentiated Permo-Carboniferous; Q = Quaternary; T = Tertiary. land Junction, Sec 2, T31N, R80W. Most of the
. Bulletin. Natural history; Natuurlijke historie. COROSAURUS ALCOVENSIS. Fig. 2. Simplified geologic map of Casper-Goose Egg-Freeland Junction area, Natrona County, Wyoming, after Fig. 1. Triassic and undiflTerentiated Permo-Triassic sediments stippled. Areas of Quaternary surficial deposits marked by dashed outlines. Faults indicated by heavy lines. G= Cam- brian; J = Jurassic; K = Cretaceous; K/J = undiflTerentiated Cretaceous and Jurassic; P = Permian; pG = Precambrian; P/C = undiflTerentiated Permo-Carboniferous; Q = Quaternary; T = Tertiary. land Junction, Sec 2, T31N, R80W. Most of the Yale Peabody Museum specimens were discovered in talus blocks beneath cliffs of the horizontal Alcova Limestone southwest of Muddy Mountain, along Corral Creek, Milne Ranch, sections 27 and 33, T31N, R79W. It is not possible to prospect directly the resistant, cliff- forming ledge of the Alcova here. Examination of talus blocks yielded occasional Corosaurus bones along exposed bedding plane surfaces. It was originally hoped that the carbonate nature of the Alcova would allow ready acid dissolution of the fossil matrix. However, while the limestone is easily dissolved, the bones themselves have been completely permineralized with calcite and are equally subject to destruction by acid. Due to the relatively dense nature of the bones, no satisfactory method of protective impregnation was found by which the fossils could be easily extracted from the matrix through chemical means. Mechanical preparation with hand and power tools was therefore utilized and, although slow and tedious as noted by both Case (1936) and Zangerl (1963), had the advantage of supplying an intimate knowledge of each fossil. Unfortu- nately, earlier crude mechanical preparation had already damaged some speci- mens. Attempts to determine the nature and extent of imbedded examples through X-radiography failed, as they did for Case (1936), because the approximately equal densities of bone and matrix furnishes lit
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