胎盤菊石

胎盤菊石（學名：），又名平盤菊石、餅菊石，是生存在晚白堊紀海洋中的一屬菊石。牠們可能是所有已知的菊石中游速最快的，透過噴水的動力來追逐獵物、逃避兩棲動物與魚類的攻擊。其化石在亞洲、歐洲和美洲都有發現。

特徵
的咬痕。]]
胎盤菊石具有緊壓的、內旋的殼，腹狹窄，有散發光彩的厚實真珠質層。牠們最大可長到50公分長，其巨大的體型和流線型的殼體使牠們在水中能快速游動。

物種
*Placenticeras bidorsatum
*Placenticeras cumminsi
*Placenticeras fritschi
*Placenticeras grossouvrei
*Placenticeras kolbajense
*Placenticeras maherndli
*Placenticeras mediasiaticum
*Placenticeras memoriaschloenbachi
*Placenticeras orbignyanum
*Placenticeras paraplanum
*Placenticeras placenta
*Placenticeras polyopsis
*Placenticeras pseudoplacenta
*Placenticeras semiornatum
*Placenticeras syrtale
*Placenticeras tamulicum
*Placenticeras vredenburgi
*Placenticeras whitfieldi

參考文獻

• Arkell et al., 1957, Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology Part L. Geological Soc. of America, Univ of Kansas Press. R.C. Moore, (Ed)
• W. A. Cobban and Hook, S. C. 1983 Mid-Cretaceous (Turonian) ammonite fauna from Fence Lake area of west-central New Mexico. Memoir 41, New Mexico Bureau of Mines&Mineral Resources, Socorro NM.
• W. A. Cobban and Hook, S. C. 1979, Collignoniceras woollgari wooollgari (Mantell) ammonite fauna from Upper Cretaceous of Western Interior, United States. Memoir 37, New Mexico Bureau of Mines&Mineral Resources, Socorro NM.
• Discovering Fossils: How to Find and Identify Remains of the Prehistoric Past (Fossils & Dinosaurs) by Frank A. Garcia, Donald S. Miller, and Jasper Burns

外部連結

• [http://paleodb.org/cgi-bin/bridge.pl?action=basicTaxonInfo&taxon_no=15403 Placenticeras] in the Paleobiology Database

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