Palaeobiological features of the coralomorph Amsassia from the Late Ordovician of South China

Abstract

Amsassia yushanensis sp. nov. occurs in the Late Ordovician Xiazhen Formation at Zhuzhai, Jiangxi Province of southeastern China. This species is characterized by typical phacelocerioid organization of modules comparable with the other Amsassia species described in recent literature. Bipartite fission, in which a parent module divided into two parts, is by far the most common type of increase in this species; tripartite and quadripartite types of axial fission do occur but are relatively uncommon. Processes of module division are similar to those of A. shaanxiensis and A. koreanensis, and also occurred in tetradiids. In A. yushanensis, restoration of coralla was occasionally accompanied by recovery of a damaged or injured module or group of modules probably following an influx of sediment, as observed in some favositoid corals. Amsassia superficially resembles Lichenaria, a representative genus of the most primitive stock of tabulate corals of Ordovician age, and has likely been mistakenly identified as Lichenaria in the North China Platform. Available information suggests that the validity of a reported occurrence of Lichenaria in the South China Platform is also questionable.