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Nautiloceras
''Nautiloceras'' is an extinct genus from the nautiloid order Nautilida,〔(Paleobiology Database ''Nautiloceras'' entry )〕 which includes the living ''Nautilus'' and its close relative ''Allonautilus''.
''Nautiloceras'' is a poorly known genus that probably belongs to the Trigonoceratidae. According to Kummel (1964) ''Nautiloceras'' is a jr synonym for ''Trigonoceras'' which was named by M'Coy in 1948. Different ages are given for the two however,〔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) )〕 with ''Nautiloceras'' being from the Upper Tournesian, about 352-345 Ma, (Lower Osage) and Trigonoceras somewhat younger, Upper Visean - Lower Serpukhovian, (Upper Meremec - Chester) with the span from about 340 to 322 Ma.
Nautiloceras 〔 may have been cyrtconic to loosely gyroconic, coiled without whorls being in contact with one another. Gyroconic forms may have had a subtriangular cross section with a broad concave venter, occupying the outer rim.
==References==
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