Flourishing chancelloriids from the Cambrian Kaili Biota of South China

Diverse chancelloriids from two sections of the Kaili Biota (Cambrian Wuliuan Stage) in Guizhou Province, China, are systematically described. A total of 25 complete individuals were collected from calcareous silty mudstones of the Cambrian Kaili Formation and are assigned to 3 genera and 6 species, including Archiasterella anchoriformis sp. nov., Chancelloria zhaoi sp. nov., C. eros, Allonnia erjiensis, Al. phrixothrix, and Al. sp. The new species Ar. anchoriformis with sclerites characterised by a large angle between two marginal-lateral rays and an obvious apical tuft represents the first unambiguous Archiasterella scleritome in South China. The C. zhaoi is dominated by a series of bilaterally symmetrical, rosette-like sclerites that composed of five or six lateral rays and a central ray. Moreover, based on a careful survey of the spatial-temporal distribution of chancelloriids (including both scleritome and isolated sclerite fossils) in South China, two flourishing ages, though may be related to preservational bias, of this metazoan group are recognised: 1) a significant diversification in the upper Stage 2 to Stage 3 and 2) a thriving in the Wuliuan Stage.