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|regnum = Animalia |phylum = Mollusca |classis = Cephalopoda |ordo = Ammonitida |subordo = Ancyloceratina |superfamilia = Protancyloceratoidea |familia = Aegocrioceratidae |genus = ''Annuloceras'' |genus_authority = Murphy ''et al'', 1995 |subdivision_ranks = Species |subdivision = *''A. summersi'' }} ''Annuloceras'' ("Ringed Horns") is an extinct genus of ammonite cephalopod. Its fossils are found in Lower Barremian sediments from California. The genus is currently placed in the family Aegocrioceratidae. ''Annuloceras'' is a heteromorph ammonite similar in form to other heteroceratids except that the early helix is more loosely wound. ''Macroscaphites'' differs in that the early portion is planispiral and tightly wound. Contemporary ''Shastoceras'', found the same strata in California, differs in lacking a coiled juvenile section. ==References== *A New Heteromorph Ammonite from the Barremian (Cretaceous) of California Michael A. Murphy, Peter U. Rodda, Patrick Embree Journal of Paleontology, Vol. 69, No. 6 (Nov., 1995), pp. 1179–1182 (abstract ) 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「Annuloceras」の詳細全文を読む スポンサード リンク
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