Chancelloriids from the Cambrian (Stage 4) Balang Lagerstätte of South China and a reappraisal of their diversification in South China

Abstract

Chancelloriids are an enigmatic group of Cambrian animals characterized by radially symmetrical bodies equipped with spiny sclerites. Although they were major components of many benthic communities, current understanding on how this group diversified during the Cambrian remains limited. Clarifying these confusions about the diversification of chancelloriids requires new information provided by new studies of previously described and/or new material. Considering the emerging scenario of chancelloriids, the sack-like chancelloriids from the Stage 4 Balang Lagerstätte are restudied on the basis of previous collections, which are herein separated from Chancelloria eros Walcott, 1920, and revised as Archiasterella acuminata nov. sp. and Chancelloriidae gen. et sp. indet. The Ar. acuminata specimen is well preserved and does show its scleritome and sclerite characters, while the Chancelloriidae gen. et sp. indet. specimen is poorly preserved and its scleritome and sclerite characters are difficult to distinguish. By combining information from previous studies and the present research, data on chancelloriid occurrences in South China indicate that chancelloriids had once diversified in the Cambrian South China, evidenced by high-level richness of sclerite-based taxa during the late Fortunian to the middle Stage 3, and of sclerite formulas during the late Stage 2 to the Wuliuan. The result is inconsistent with the recent viewpoint that there were two flourishing ages of chancelloriids in South China. Although more evidence is needed to support our results, the present study offers insights in understanding the evolutionary dynamics of chancelloriids.