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''Balticeras'' is an involute, discoidal Upper Jurassic (Oxfordian) ammonite (order Ammonitida) found in England, Germany, and Switzerland, belonging to the Perisphinctidae. The shell is strongly embracing, tending to be oxyconic (sharp rimmed). Sides are gently curved, converging on a narrow to sharp ventral rim. ''Balticeras'' is considered by some to be a subgenus of ''Ringsteadia'' which in contrast is more evolute, with ribbed inner whorls. Both are included in the Pictoniinae, a subfamily established by Spath, 1924, for large ammonites within the Perisphinctidae, tending to develop smooth middle and outer whorls. ==''References''== ;Notes ;Bibliography *Arkell, et al., 1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L (Ammonoidea). Geol. Soc. of America and Univ. Kansas Press. 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「Balticeras」の詳細全文を読む スポンサード リンク
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