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''Ptychagnostus'' is an extinct genus of blind trilobite that lived during the Cambrian period, part of the order Agnostida. Ptychagnostidae generally do not exceed ten millimetres in length.〔 Their remains are sometimes found in the otherwise empty tubes of the polychaete worm ''Selkirkia''. It probably lived in the water column. Its major characteristics are lack of eyes, two lobes on the glabella, and three lobes on the pygidium.〔Coppold, Murray and Wayne Powell (2006). ''A Geoscience Guide to the Burgess Shale'', p.56. The Burgess Shale Geoscience Foundation, Field, British Columbia. ISBN 0-9780132-0-4.〕 ==Species== *''Ptychagnostus aculeatus'' *''Ptychagnostus akanthodes'' *''Ptychagnostus atavus'' *''Ptychagnostus cassis'' *''Ptychagnostus ciceroides'' *''Ptychagnostus cuyanus'' *''Ptychagnostus fissus'' *''Ptychagnostus germanus'' *''Ptychagnostus gibbus'' *''Ptychagnostus hybridus'' *''Ptychagnostus intermedius'' *''Ptychagnostus michaeli'' *''Ptychagnostus praecurrens'' *''Ptychagnostus punctuosus'' *''Ptychagnostus seminula'' 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「Ptychagnostus」の詳細全文を読む スポンサード リンク
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