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''Tainonautilus'' is an extinct coiled cephalopod that lived during the Permian and Early Triassic which is included in the nautiloid family Tainoceratidae. ''Tainonautilus'' has an evolute shell with a subquadrate whorl section. Flanks and outer rim (venter) are flat. The umbilicus is wide and deep; umbilical shoulders have a prominent keel. The sides bear curved retrograde ribs or folds that slant to the rear going from the inner (umbilical) rim to the outer (ventral). The venter, which forms the outer rim has a smooth median sulcus. The siphuncle is subventral, lying near but not on the outer margin. ''Tainonautilus'' has been found in the Alps in Europe and in the Salt Range in Pakistan. ==''References''== * Kummel 1964, Nautiloidea—Nautilida. Treatise on Invertebrate Paleontology Part K Mollusca 3. Geol Soc of America and Univ Kansas Press; Teichert and Moore (eds) 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「Tainionautilus」の詳細全文を読む スポンサード リンク
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