DOUBLURE OF PLAGIOLARIA NANDANENSIS CHANG (DEVONIAN TRILOBITA) IN GUANGXI

Many calcareous phacopid specimens have been reported from the U.S and Europe. In China phacopid specimens representing the genera Phacops and Plagiolaria have been reported from Lower and Middle Devonian Mudstones in the Nandan district, Guangxi.The name Plagiolaria was introduced by Kegel (1952) as a new name for Plagiops Kegel, 1932, based on Phacops plagiophthalmus Reinh. Richter 1865. Species of the genus have been reported from Germany, Viet-Nam, Thailand and China. The species studied here is Plagiolaria nandanensis from the lower Middle Devonian Tangding Formation in the Luofu district, Nandan County, Guangxi Province. Specimens are usually preserved in mudstone; some specimens are silicified. The trilobite species is associated with tentaculites and brachiopods. Previous descriptions largely based on internal moulds are therefore inexact as far as the exterior morphology is concerned. In 1987, Han Nairen, Zhou Youmin and Wang Jialing collected many specimens of P. nandanensis in order to study the moulting. Among the specimens were two silicified thoracopygidia. In 1989, Professor Li Youxing provided the authors with a perfect silicified ventral specimen of P. nandanensis Chang in which the doublure of the thorax is well exposed (Pl.1, fig.3). In this specimen, the doublure of the first nine pleural ends is preserved. In 1987, Han and others collected several specimens exposing thoracic doublure.

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Clc Number:

Q915.819.1