Three species of Pagodia (Corynexochida, Trilobita) from the Furongian (Cambrian) of northern Anhui, China and their intraspecific variation

Abstract

More than one thousand cranidia, librigenae, and pygidia of the trilobite Pagodia were collected from the Cambrian (upper Jiangshanian through Stage 10) at Fenghuangshan in northern Anhui, China. They were identified as Pagodia lotosWalcott, 1905, Pagodia depressa (Walcott, 1905), and Pagodia biaWalcott, 1905. Based on one rare nearly complete exoskeleton of P. depressa and comparisons among the three species of Pagodia, the redefinition for those species is attempted as follows. Pagodia lotos: Glabella rectangular, slightly convergent anteriorly; anterior border ridge-like, anterior border furrow deep; pygidium semicircular, axis tapered rearward, with 4 axial rings and a terminal piece. P. depressa: Cranidium subquadrate, highly convex; glabella cylindrical, convergent anteriorly; pygidium semicircular. P. bia: Glabella rectangular, constricted in the midlength; fixigena wide (tr.); anterior border very narrow (sag.) and ridge-like; pygidium semicircular with wide borders; pygidial axis ended closer to the pygidial border furrow. We also discuss their intraspecific variations, commonly seen on the exfoliated specimens: palpebral ridge evident or obliterated, the length (sag.) of anterior area variable, the decoration of exoskeleton surface (with granules variable in size, convex or pitted).