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''Obinautilus'' is an extinct genus of shelled cephalopod that has been variously identified as an argonautid octopod〔Ozawa, T. & S. Tomida (1996). Occurrence of ''Aturia coxi'' (Cephalopoda; Nautilida) from the uppermost Miocene of Japan and its implication for late Miocene marine climate in the northwestern Pacific. ''Journal of Paleontology'' 70(5): 795–798. 〕〔〔〔Martill, D.M. & M.J. Barker (2006). A paper nautilus (Octopoda, ''Argonauta'') from the Miocene Pakhna Formation of Cyprus. ''Palaeontology'' 49(5): 1035–1041. 〕〔Strugnell, J.M., A.D. Rogers, P.A. Prodöhl, M.A. Collins & A.L. Allcock (2008). The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses. ''Cladistics'' 24(6): 853–860. 〕〔Strugnell, J. & A.L. Allcock (2010). Co-estimation of phylogeny and divergence times of Argonautoidea using relaxed phylogenetics. ''Molecular Phylogenetics and Evolution'' 54(3): 701–708. 〕 or a nautilid.〔〔Ward, P. (1980). Comparative shell shape distributions in Jurassic–Cretaceous ammonites and Jurassic–Tertiary nautilids. ''Paleobiology'' 6(1): 32–43. 〕〔Teichert, C. & T. Matsumoto (2010). The Ancestry of the Genus ''Nautilus''. In: W.B. Saunders & N.H. Landman (eds.) ''Nautilus: The Biology and Paleobiology of a Living Fossil''. Springer. pp. 25–32. 〕〔(UMUT CM 08493: ''Obinautilus pulchra'' Kobayashi, 1954 ). The University Museum, The University of Tokyo.〕〔Eyden, P. (2010). (Fossil Octopuses ). TONMO.〕 It is known from the Late Oligocene to Pliocene of Japan.〔Saul, L.R. & C.J. Stadum (2005). Fossil argonauts (Mollusca: Cephalopoda: Octopodida) from Late Miocene siltstones of the Los Angeles Basin, California. ''Journal of Paleontology'' 79(3): 520–531. 〕 The shell is discoidal and very involute, with rapidly expanding and compressed whorls, fine radial ribs, a rounded venter with a shallow furrow, and almost closed umbilicus. Based on the examination of ''O. pulcher'' fossils from the Oligocene, the ''Tremoctopus''–''Argonauta'' divergence has been estimated to have occurred at least 29 million years ago.〔Strugnell, J., J. Jackson, A.J. Drummond & A. Cooper (2006). Divergence time estimates for major cephalopod groups: evidence from multiple genes. ''Cladistics'' 22(1): 89–96. 〕 ==Species== Two species are recognised in the genus.〔 *''Obinautilus awaensis'' (originally described as ''Argonauta awaensis''〔Tomida, S. (1983). Two new fossil ''Argonauta'' and firstly discovered ''Aturia coxi'' Miller from the late Tertiary of Boso Peninsula, Japan. ''Muzunami-shi Fossil Museum Bulletin'' 10: 107–116.〕) — Pliocene (possibly also latest Miocene〔) Upper Senhata Formation of Bōsō Peninsula, Japan〔 *''Obinautilus pulcher'' (sometimes spelled ''O. pulchra''〔〔) — Late Oligocene Nichinan Formation of Japan〔 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「Obinautilus」の詳細全文を読む スポンサード リンク
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