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|image = Aulacostephanidae - Aulacostephanus yo.JPG |image_caption = Fossil shell of ''Aulacostephanus yo'' from France, on display at Galerie de paléontologie et d'anatomie comparée in Paris |regnum = Animalia |phylum = Mollusca |classis = Cephalopoda |subclassis = Ammonoidea |ordo = Ammonitida |familia = Aulacostephanidae |genus = ''Aulacostephanus'' }} ''Aulacostephanus'' is an extinct ammonoid cephalopod genus from the Upper Jurassic Kimmeridgian belonging to the perisphinctacean family Aulacostephanidae. ''Aulacostephanus'' produced a discoidal, strongly ribbed,evolute shell of moderate size, reaching diameters of 16 cm (~6.5in.), or so. Ribs diverge in pairs and threes from nodes on the umbilical shoulder and extend radially outward onto the ventro-lateral shoulder, but do not cross the venter, (the outer rim). Sides are flat, the venter steeply rounded, with an open bend or median groove running down the middle. Clutches of eggs attributed to this genus have been discovered in the Kimmeridge Clay. ==References== ;Notes ;Bibliography * Treatise on Invertebrate Paleontology, Part L, Ammonoidea. R.C. Moore (Ed). Geological Society of America, 1957. 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「Aulacostephanus」の詳細全文を読む スポンサード リンク
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