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| image = | regnum = Animalia | phylum = Mollusca | classis = Cephalopoda | subclassis = Nautiloidea | ordo = Pseudorthocerida | ordo_authority = Barskov 1963, from Flower & Caster, 1935 }} Pseudorthocerida are generally straight longiconic nautiloids with a subcentral to marginal cyrtochoanitic siphuncle composed of variably expanded segments which may contain internal deposits that may develop into a continuous parietal lining.(Sweet 1964). Cameral deposits are common and concentrated ventrally. Apices typically have a slight to moderate exogastric curvature The Pseudorthocerida are included in a broad in-group of generally orthoconic cephalopods known as the Orthoceratoidea (Kroger 2008) along with the Ascocerida, Dissidocerida, Lituitida, and Orthocerida. The Pseudorthocerida, Ascocerida, and Dissidocerida all have a cap-shaped apex, shared with Nautilids and Actinocerids, placing them in the "palcephalopoda". The Lituitida and Orthocerida share their spherical or bulbous apices with the Bactritida and Ammonoidea, by which they are included in the "neocephalopoda" The Pseudorthocerida were among the last living orthoconic nautiloids. One family, the Trematoceratidae, survived into the Triassic Period. ==Taxonomy== 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「Pseudorthocerida」の詳細全文を読む スポンサード リンク
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