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Tannudiscus
''Tannudiscus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the upper Lower Cambrian, with remains found in Canada (Newfoundland), China (Gansu), The United Kingdom (England), and the Russian Federation (Tuva, Gorno-Altayskaya).〔 == Taxonomy == The Weymouthiid family shows a trend of shortening the occipital ring. In ''Chelediscus'' and ''Tannudiscus'' the occipital ring is entirely obliterated as in the Agnostina suborder. ''Tannudiscus'' has some other characters it shares with the Agnostina, such as a glabella consisting of two lobes, the occipital ring divided into basal glabellar lobes, both the glabella and the pygidial axis isolated from border furrow, and undivided pygidial axis. It is therefore considered likely that the Agnostina descended directly from a species assignable to ''Tannudiscus''. The earliest known Agnostina is ''Archaeagnostus'' (Peronopsidae).〔 According to Cotton and Fortey (2005) Tannudiscus is polyphyletic.
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「Tannudiscus」の詳細全文を読む
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