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''Cunningtoniceras'' is a stocky acanthoceratid ammonite from the upper Cenomanian stage of the late Cretaceous of the western U.S., found e.g. in Arizona and New Mexico. ''Cunningtoniceras'' was proposed by Collignon, 1927, for ribbed, evolute ammonites having a quadrangular whorl section; umbilical, inner and outer ventrolateral, and siphonal (i.e. mid-ventral) tubercles; a venter with a multiplication of ribs and tubercles, or one or the other. Ornament weakens with age except for the inner ventrolateral tubercles, which enlargen. Cobban, Hook & Kennedy, 1989, distinguish ''Cunningtoniceras'' Collignon from ''Euomphaloceras'' Spath 1923, the two having been previously regarded as synonymous. In fact ''Cunningtoniceras'' is described in the Treatise L, 1957 as a synonym of ''Euomphaloceras'', noted as having three rows of small tubercles on a broad flat venter. Although ''Cunningtonicaras'' and ''Euomphaloceras'' share many characters, both belonging to the Acanthoceratidae, they are distinguished by the nature of the first lateral lobe of their respective sutures. The first lateral lobe of species ultimately assigned to ''Cunningtonicaras'' are narrow and bifid, contrasting with the broad and deeply bifid lobes of ''Euomphalooceras''. ==References== * W.J. Arkell, et al. 1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L. Geological Society of America, R.C. Moore (ed). * W.A. Cobban, S.C. Hook & W.J.Kennedy, 1989. Upper Cretaceous rocks and ammonite faunas of southwestern New Mexico. Memoir 45, New Mexico Bureau of Mines & Mineral Resources. 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「Cunningtoniceras」の詳細全文を読む スポンサード リンク
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