|
''Proplacenticeras'' is a discoidal ammonite from the lower part of the Upper Cretaceous and precursor of the overall similar ''Placenticeras''. The shell is compressed, with flat or slightly convex sides and narrow flat venter, with or without slightly conical umbilical tubercles, ventrolateral clavi and crescentic ribs on outer part of sides. Sutures are with fewer auxiliary elements than on latter ''Placenticeras''. Species in sequential order, starting with the oldest, include ''P. sutherlandbrowni'', ''P. stantoni'', ''P. pseudoplacenta'', ''P. fritschi'' and ''P. kaffrarium''; sometines identified as ''Placenticeras''. ''Proplacenticeras'' has a fairly wide distribution and is known from the western United States and Canada, Mexico, France, Spain, Angola, Israel, Madagascar, India and NE Central Asia. ==References== * W.J. Arkell, et al., 1957. Mesozoic Ammonoidea, Treatise on Invertebrate Paleonotology Pat L Mollusca 4. Geological Society of America and University of Kansas Press. *William A Cobban & Stephen C. Hook. 1979. ''Collignoniceras woollgari woollgari'' (Mantell) ammonite fauna from Upper Cretaceous of Western Interior, United States. Memoir 37. New Mexico Bureau of Mines & Mineral Resources. * ( Proplacenticeras ) in Fossilworks. 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「Proplacenticeras」の詳細全文を読む スポンサード リンク
|