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The Kirengellids are a group of problematic Cambrian fossil shells of marine organisms. The shells bear a number of paired muscle scars on the inner surface of the valve. These fossils have conventionally been regarded as monoplacophoran molluscs, and possibly ancestral to gastropods or cephalopods.〔e.g. 〕 They were presumed to be exogastric on the presumption that their larger muscle scars were anterior, but it may be dangerous to compare these scars with molluscan musculature.〔 In any case, they coiled in the opposite direction to ''Romaniella''.〔 However, their calcitic shells, the position of the muscle scars, and putative association with secondary shell elements, make a brachiopod affinity possible, by analogy with the mobergellans: a group of phosphatic shells from the same time period, with a similar set of muscle scars.〔 There is also strong similarity to the contemporary brachiopod group, the Craniopsids. In the case of this diagnosis, a simple lophophore apparatus is postulated to sit between the muscle scars and the edges of the shell. ==Included taxa== After 〔 * ''Kirengella'' Rozov, 1968 (Upper Cambrian) * * ''Kirengella ayaktchica'' - type species * * ''Kirengella expansus]'' * * ''Kirengella oregonensis'' * * ''Kirengella pyramidalis'' * * ''Kirengella washingtonense'' * ''Hypseloconus'' (Upper Cambrian) * ''Lenaella'' (Tremadoc / Lower Ordovician) * ''Nyuella'' (Tremadoc / Lower Ordovician) * ''Romaniella'' (Arenig / late Lower Ordovician) * ''Moyerokania'' (Arenig / late Lower Ordovician) * ''Angarella'' (Arenig / late Lower Ordovician) * ''Pygmaeoconus'' (Llanvirn / early Middle Ordovician) 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「Kirengellidae」の詳細全文を読む スポンサード リンク
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