Diversity Of Cnidarians From The Cambrian Fortunian Xixiang Lagerst(?)tten,South China

The origin and early evolution of cnidarians are significant for understanding themselves and also bilaterians.As the background of Cambrian radiation,the diversity and richness of cnidarians peaked at the Cambrian Fortunian stage.This study mainly reported some new fossil materials and some new cognition was found.Furthermore,this study described and summarized the fossils of early Cambrian cnidarians in south China,and introduced the body plan,radial symmetry,life habits,and life history of different types of cnidarians.This study described several embryos,larva or adult stage specimens of Olivooides multisulcatus.The new materials showed the lobe of the embryo was distinct triangular thickening correspond to the adult.And a new O.multisulcatus with 22 crests of postembryonic tissue,the largest number of transverse crests found so far,was reported.Besides,there were a few newfound fossils of the whole apical complement covering the morphological integrity of Qinscyphus.The discovery of the apical complement of the Qinscyphus is novel and essential for completing the external morphology of the early medusozoan fossils.This paper also provides important implications for the study of early evolution and ecology.As for Quadrapyrgites,I conducted a more in-depth study.Firstly,based on observing numerous embryonic fossils at different developmental stages,I tentatively reconstructed the development sequence of lobes in the apertural region.Secondly,rare adult specimens with partial damage to the oral sheath reveal an internal funnel-shaped structure directly connected to the oral part.Moreover,this study compared different specimens with 1-14 crests by dig TPS,concluding the allometric and unipolar growth of Quadrapyrgites.Finally,this study also reported a new specimen having morphology well comparable with the previously reported specimens of Quadrapyrgites quadratacris,except that it is pentamerous.It demonstrated that intraspecific variation had appeared in the Fortunian scyphozoans and it was not reliable to determine the classification of fossils by different radial symmetry numbers.This study found two unidentified fossils with pentaradial symmetry in the Zhangjiagou section with perradial ridge,constricting zone,and oral arms.They may have a close relationship with scyphozoan.This study described several internal molds of Anabarites.The new specimens preserved the apex,the aperture with three lobes,and three longitudinal grooves initiating apically rather than adapically as previously reported.This work enriched the morphology of anabaritids,casting doubt on the previous proposition that anabaritids originated from a cylindrical tubular ancestor.It is proposed here that a triradial symmetry may have been established in very early ontogenetic stages of some anabaritids;furthermore,the aperture with three lobes resembles those of olivooids and thus supports a possible close relationship between anabaritids and olivooid scyphozoans.