Trilobites from the Upper Ordovician Tangtou Formation, Jiangsu Province, China

Abstract

ABSTRACTForty-one species assigned to thirty-seven named genera of trilobites are described from the Tangtou Formation at Tangshan and Lunshan, in Jiangsu Province, SE China.Nankinolithus nankinensisLu, the Zone fossil of the upper part of the Formation, is abundant. Many Tangtou Formation species occur also in the Huangnehkan, Linhsiang and Chiencaokou formations, and all are considered to be of early Ashgill age. The trilobites are closely related to those of theStaurocephalus clavifronsZone (Rawtheyan) of Poland, demonstrating the long duration and wide extent of deeper water faunas. There are also close links with the Ashgill faunas of Central Asia.One new species,Amphitryon cheni, is established. The following morphological features are described: a small remopleuridine hypostome is unlike any other in construction;Nileus transversusretains genal spines to full grown size in some specimens, but loses them in others; the hypostome lacks the posteromedian cusp of other species. The hypostome ofParaphillipsinellais strongly styginid in conformation, and unlike that ofPhillipsinella. Telephina convexais the only species known with three spines on the librigena. The arrangement of pits inNankinolithus nankinensis, the type species, is described, including illustrations of the irregularities which occur in every fringe. A small bulb at the tip of the hypostome ofOvalocephalus(=Hammatocnemis) bears two backwardly pointing spinules, one above the other, on the vertical posterior margin. Three types of protaspides, and numerous meraspid parts are described.