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''Wardoceras'' is an extinct nautiloid genus from the late Early Ordovician of Western Utah, assigned to the orthocerid family, Michelinoceratidae Shells of ''Wardoceras'' are smooth and orchoconic, with a circular cross section and small subcental siphuncle, the segments of which are ventrally straight and dorsally slightly expanded into the camerae. The siphuncle is completely encircled internally by a thin lining that thickens and thins rhythmically so as to slightly thicken just forward of the septal necks, suggesting an origin in annular deposits. Cameral deposits are well developed and are thick,almost filling the ventral portion of the more apical chambers but also found in dorsal chambers as well. ''Wardoceras'' is represented by the type species, ''Wardoceras orygoforme'' which is known only from the holotype, a 97mm long portion of a phragmocone 13.5mm in diameter at the anterior end; found 25.9m (85ft) above the base of the Wahwah Limestone, section J,Ibex area, Utah. ''Wardoceras'' is named for Jane Shaw Ward, author of the Tajar stories. See also ''Tajaroceras'', ''Rangeroceras'', and ''Veneficoceras'' ==References== * Stephen C. Hook and Rousseau H. Flower 1977. Late Canadian (Zones J,K) Cephalopod Faunas from Southwestern United States. Memoir 32, New Mexico Bureau of Mines and Mineral Resources. * Sepkoski, J.J. Jr. 2002. A compendium of fossil marine animal genera. D.J. Jablonski & M.L. Foote (eds.). ''Bulletins of American Paleontology'' 363: 1–560. (Sepkoski's Online Genus Database (CEPHALOPODA) ) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Wardoceras」の詳細全文を読む スポンサード リンク
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