The trilobite Pseudoblackwelderia lubrica (Damesellidae) from the Cambrian (Guzhangian) Changhia Formation of Northern Anhui, China, and its potential sexual dimorphism

Abstract The North China type Cambrian System is well developed in northern Anhui Province. A large number of specimens of the trilobite Pseudoblackwelderia lubrica were collected from the Guzhangian (later Cambrian) Changhia Formation at Fenghuangshan in northern Anhui, China, prompting a redefinition of the species. Our emended diagnosis includes: a cone-shaped glabella that is broadly to acutely rounded anteriorly; three pairs of glabellar furrows; the preglabellar field being absent or very short; the librigena with a narrow lateral border, a broad general field and long genal spine; the pygidium with four rings and a terminal piece on the axis; six or seven pairs of pygidial spines with the anterior five pairs being short, the posterolateral pair being long and stout, the seventh pair being small or absent. The new specimens suggest that Neimengguasps is a junior synonym of Pseudoblackwelderia. Moreover, the presence or absence of paired spines on the posterior margin of pygidium is attributed to potential sexual dimorphism. Qianping Lei [cicelyapple@126.com], Nature Department, Changzhou Museum, Changzhou, Jiangsu Province, 213022, PR China Qing Liu [qingliu1029@yeah.net], Room 104, Unit A, Building Six, Fenghuanghu No. 1, Xinbei District, Changzhou 213125, PR China Shanchi Peng [scpeng@nigpas.ac.cn], State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing 210008, China; Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China.