MOLTING IN PLAGIOLARIA (TRILOBITA) FROM T HE LOWER DEVONIAN OF CHINA

Plagiolaria nandanensis is a zonal index-fossil from the Lower Devonia n of Nandan, Guangxi, China. Strata of this age yield numerous exuvies of trilobites. These exuvies show that the break of the dorsal exoske leton in P. nandanensis started with the separation of the thorax and the cephalon; the animal shed the hypostoma and crawled forward, lifti ng up the cephalon and then turning it upside down. Sometimes, during a final stage, the thorax and the pygidium cleaved apart. Moulting in Plagiolaria nandanensis represents the mode of moulting in small-eyed Phacopids.