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・ Petar Gračanin
・ Petar Grašo
・ Petar Grbić
・ Petar Grgec
・ Petar Gudev
・ Petar Hadzi Boskov
・ Petar Hektorović
・ Petaloconchus erectus
・ Petaloconchus floridanus
・ Petaloconchus glomeratus
・ Petaloconchus interliratus
・ Petaloconchus intortus
・ Petaloconchus mcgintyi
・ Petaloconchus nigricans
・ Petaloconchus varians
Petalocrinidae
・ Petalodontidae
・ Petalodontiformes
・ Petalodus
・ Petalomyrmex
・ Petalonema
・ Petalonema alatum
・ Petalonyx
・ Petalonyx linearis
・ Petalonyx nitidus
・ Petalonyx thurberi
・ Petalophthalmidae
・ Petalophyllaceae
・ Petalophyllum ralfsii
・ Petalopoma


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Petalocrinidae : ウィキペディア英語版
Petalocrinidae

Petalocrinidae is an extinct family of cladid crinoid from the Early Ordovician to Lower Devonian. Fossils of petalocrinoids have been found in China, Europe and the United States.
All petalocrinoids have five, flattened arms formed through the fusion of the branches of the ancestral crinoid arm, an Ordovician crinoid possibly similar to the Silurian ''Gissocrinus'' or ''Arachnocrinus''. The shape of these fused arms varies from genus to genus, and from species to species. The upper surface of the arms had distinctive patterns of grooves which are thought to have born captured food particles towards the mouth. The purpose of the arms, themselves, remain unknown, though, some researchers suspect that they may deterred predators by presenting a would-be attacker with a largely inedible chunk of calcite.
==Genera==


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「Petalocrinidae」の詳細全文を読む



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