Revising some fossil clam shrimps (Branchiopoda: Diplostraca: spinicaudata) from the Upper Triassic in Yunnan Province and chongqing city, southwestern china

Abundant Triassic spinicaudatans from China have been commonly assigned to the genus Euestheria Depéret & Mazeran. However, recent SEM-based studies have revealed that many of them do not belong to euestherids, as evidenced by their distinctive micro-ornamentations, revealed by scanning electron microscopy (SEM). In this study, we describe two spinicaudatan species, Polygrapta yipinglangensis comb. nov. and P. dazuensis comb. nov., which were previously identified as members of Euestheria from the Upper Triassic Ganhaizi and Xujiahe formations in south-western China. The carapace ornamentations of these species exhibit fine polygonal reticulations in the upper parts, which gradually transform to linear arrangements and radial lirae at the ventral regions. Based on these features, they are classified into Polygrapta Novojilov. Although the two species exhibit morphological similarities, they can be distinguished by variations in reticulation size and the width of linear arrangements in their marginal areas.