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The Crioceratidae constitute a family of loosely to closely coiled Ammonitida included in the Ancyloceratoidea that lived during the Early Cretaceous; characterized by ''Crioceratites'' and other genera such as ''Hoplocrioceras'' and ''Paracrioceras''. The Crioceratidae are gyroconic, coiled in a plane, generally with space between the whorls although in some like ''Balearites'' the whorls are barely in contact. Although distinct in character and not truly heteromorphic the Crioceratidae were included in the American TreatisePart L, 1957, in the Ancyloceratidae as the subfamily Crioceratinae. It is now considered a distinct family as originally proposed by Wright 1952 with the Acrioceratidae, proposed by Vermeulen (2004), a transition between the two. Other genera in the Crioceratidae include ''Aegocrioceras'', ''Menutheocrioceras'', and ''Shasticrioceras. ==References== * W.J. Arkell, et al, 1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L, Mollusca 4. Geological Society of America and University of 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「Crioceratidae」の詳細全文を読む スポンサード リンク
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