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| regnum = Animalia | phylum = Mollusca | classis = Cephalopoda | subclassis = Ammonoidea | familia = Psiloceratidae | genus = ''Psiloceras'' | genus_authority = Hyatt, 1867 |subdivision_ranks = Species 〔(Paleobiology Database - Psiloceras ). 2014-05-29.〕 |subdivision = * ''P. planorbis'' (J.C. Sowerby, 1824) (type) synonym ''Ammonites planorbis'', ''A. sampsoni'', ''P. sampsoni'' * ''P. becki'' * ''P. brevicellatum'' * ''P. calliphylloides'' * ''P. calliphyllum'' Neumayr, 1879 synonym ''Aegoceras calliphyllum'' * ''P. costosum'' * ''P. distinctum'' * ''P. erugatum'' * ''P. hagenowi'' * ''P. marcouxi'' Guex, Taylor, Rakus & Bucher, 1998 * ''P. minillaensis'' von Hillebrandt, 2000 * ''P. naumanni'' * ''P. pacificum'' Guex, 1980 * ''P. polymorphum'' Guex, 1980 * ''P. plicatulum'' (Quenstedt, 1883) synonym ''Ammonites plicatulus'' * ''P. primocostatum'' von Hillebrandt, 2000 * ''P. psilonotum'' * ''P. sampsoni'' * ''P. spelae'' Guex, Taylor, Rakus & Bucher, 1998 * ''P. spelae tirolicum'' von Hillebrandt & Krystyn, 2009 * ''P. tenerum'' * ''P. tibeticum'' Yin et al., 2007 * ''P. tilmanni'' Lange, 1925 }} ''Psiloceras'' is an extinct genus of cephalopod belonging to the ammonite subclass. ''Psiloceras'' fossils are commonly found at Watchet, Somerset, England. Here smooth-shelled ''Psiloceras planorbis'' (along with other species) are to be found as usually flattened fossils in the Blue Lias. Unlike most earlier ammonites, which had complex shell shapes and ornamentation, ''Psiloceras'' had a smooth shell. == Taxonomy == All Ammonites, with the sole exemption of the genus ''Psiloceras'' were wiped out at the Triassic–Jurassic extinction event (201.3 million years ago). Hence all ammonites that lived during the Jurassic and Cretaceous are descendants of ''Psiloceras''.〔 Most authors assume that ''Psiloceras'' descended from the Phyllocerataceae. ''P. spelae'' is probably the earliest species of ''Psiloceras''. 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「Psiloceras」の詳細全文を読む スポンサード リンク
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