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|image = Ataxioceratidae - Ataxioceras conditum.JPG |image_caption = Fossil shell of ''Ataxioceras conditum'' from Germany, on display at Galerie de paléontologie et d'anatomie comparée in Paris |regnum = Animalia |phylum = Mollusca |classis = Cephalopoda |subclassis = Ammonoidea |ordo = Ammonitida |superfamilia = Perisphinctaceae |familia = Ataxioceratidae |genus = ''Ataxioceras'' |genus_authority = |subdivision_ranks = |subdivision = }} ''Ataxioceras'' is an extinct Ammonite cephalopod genus confined to the Upper Jurassic of Europe, included in the superfamily Perisphinctaceae. Previously ''Ataxioceras'' was assigned to the Perisphinctidae but has now been placed in the Ataxioceratidae for which it is the type genus. These fast-moving nektonic carnivores lived during the Jurassic period, from 161.2 to 150.8 Ma. 〔 (The Paleobiology Database )〕 ==Description== The shell is evolute, strongly ribbed and miderately umbilicate. Primary ribs, on the order of 32 -36 per whorl, are sharp and widely spaced, originate at the unbilical shoulder. Secondary ribs form about mid flank, generally by trifurcation, but sometimes quadrafurcation (splitting into threes or sometimes fours) of the primaries. The umbilicus is about 0.4 the shell diameter. 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「Ataxioceras」の詳細全文を読む スポンサード リンク
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