Two species of Tsinania (Trilobita, Corynexochida) from upper Furongian (Cambrian) of northern Anhui, China and their intraspecific variation

Abstract

Hundreds of specimens of the trilobite Tsinania were collected from the Cambrian (upper Jiangshanian through Stage 10) at Fenghuangshan in northern Anhui, China, and were identified as Tsinania canens (Walcott, 1905) and Tsinania dolichocephala (Kobayashi, 1933). Comparisons between these two species and others referred to Tsinania, allow the redefinition of the two species. Fourteen synonyms and thirteen synonyms have been incorporated into T. canens and T. dolichocephala respectively. The key diagnosis of T. canens includes: the preglabellar field is flat, relatively short (sag.), has a slightly to obviously angular anterior margin; pygidium is rounded triangular and strongly convex; pygidial border is absent or very narrow. The key diagnosis of Tsinania dolichocephala comprises: the glabella is moderately convex with flat anterior part and convex posterior part (sag.); anterior border is relatively long (sag.), rounded to sharply angulated; pygidium is rounded triangularly with a wide, concave border. Upon such diagnoses, the potential intraspecific variations (e.g., the angularity of the anterior margin, the triangularity of the pygidium, and the width of the pygidial border) of the two species are discussed and listed. The late ontogeny of both species is described to further support the intraspecific variations.