Exuviation of Trilobite Protoryctocephalus Arcticus from the Cambrian Tsinghsutung Formation of Guizhou Province
详细信息
- 责任者：Sun Zongyuan (College of Resource and Environment ; Guizhou University ; Guiyang 550003 ; China) ; Yang Xinglian
- 刊名：Acta Palaeontologica Sinica
- 出版年：2013
- 卷期：52(2)
- 关键词：三叶虫纲 ; Trilobita ; 贵州 ; Guizhou Province
- 页码：p.256-264
- 图表：illus., 1 table, 39 refs.
- 分类号：1102
- issnNo：ISSN0001-6616
- isbnNo：CN32-1188/Q
摘要
The shelling processes of trilobites are important for ontogeny.Moulting specimens of Protoryctocephalus arcticus(Geyer and Peel,2011) are described here.They were collected from the Cambrian age Tsinghsutung Formation,Guizhou.Their cephalon,thorax and pygidium are preserved,and thoracic and pygidial shields are articulated.The trilobite exuvial configuration emerged after the following:1)The trilobite bent the cephalon downwards and upwards.The water resistance caused by the pressure on both sides of free cheeks is significantly larger than that on cranidium.This pressure may lead to fissure on the facial sutures,and then seawater drip into the cephalon through the fissure.This increases the size of new cephalon making it to lose the connection between the old cranidium and the new cranidium through the water pressure.2)The trilobite body,with the old thoracopygon and other connected parts,crawls forward,separates from the old cranidium in a short distance.3)The trilobite,through in different ways,crawls from the old shell.This paper focuses on the following:Why does their cephalon crack? Why is it that their thoracic shield and pygidial shield do not separate? How does the direction of their cephalon’s movement influence their old shells’ preservation? What function does the water pressure perform in the process of exuviations? The exuvial materials of Protoryctocephalus arcticus(Geyer and Peel,2011) provide new data for studies on systematic evolution and onto-geny of related trilobites.
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