寒武纪三叶虫Oryctocephalus indicus（Reed，1910）的蜕壳

描述了产于黔东南剑河县中寒武统凯里组中上部的19块中寒武统底部标志化石--印度掘头虫Oryctocephalus indicus(Reed,1910)蜕壳标本,其中大部分缺失头盖,其余外壳保存完好.对其蜕壳过程进行了探讨,认为蜕壳程序如下:头甲以小于90°角下弯,导致背壳沿头、胸接合处裂开;面线张开,自由颊与头盖裂开;虫体恢复平伸状态,头盖旋转;三叶虫携老壳向前爬行,并将已与自由颊和胸甲裂开的头盖顶翻于头甲前方;虫体继续向前爬行,并将头盖扒向两侧;虫体向前爬行并不断颤动,最终脱掉老壳.被脱掉的老壳胸尾相连,腹边缘-唇瓣板与自由颊基本位于原位,与"Phacopid式蜕壳"或"Salter式埋藏"明显不同.

Moulting of the Cambrian Trilobite Oryctocephalus Indicus (Reed,1910)

Nineteen specimens of Oryctocephalus indicus(Reed,1910) from the middle-upper part of Kaili Formation of Middle Cambrian in Jianhe County,southeastern Guizhou,South China,which are interpreted as exuvial configurations,are described.Most of them are missing cranidium,remains of the articulated exoskeleton are in original relation.The series of events which may have resulted in the production of these configurations are as follows:(1) The trilobite flexed the cephalon downward throuth a certain angle less than ninety degrees.During this flexing downward,the cephalon splited from the thorax as well as the facial suture opened,so that the free cheeks disarticulated from the cranidium.(2) The animal regained its planar orientation and resulted in the old cranidium rotated.(3) The trilobite crawled forward with the old exoskeleton and overturned the cranidium to inverted in front of the cephalon.(4) The inverted cranidium was pushed aside by the crawled forward animal.(5) The animal continued to crawl forward,kept shaking and withdrew from the old exoskeleton.Finally,the old exoskeleton was shed.On the exuviae,the thorax joined up with pygidium,the rostral-hypostomal plate and free cheeks located at their original site.It is different from the "Phacopid mode of ecdysis"or "Salterian embedding".