Systematic Palaeontology Of Porifera Of Chengjiang Biota,Yunnan,China

As the oldest metazoans sponges have a long history and are of the most important for deciphering the origin and evolution of metazoans.Sponges represent one of the major components in the Chengjiang Biota(Cambrian series 2,Stage 3)Although the diversity and the palaeobiological and environmental significance of Chengjiang sponge fossils have been discussed extensively,abundant new sponge fossils have been collected by the Yunnan University and Chengjiang Fossil Museum in recent years.New information obtained from these specimens provides a better understanding of the early sponges during the evolutionary history.More than 3400 Chengjiang sponge specimens were examined.This thesis mainly focuses on the systematic palaeontology of Chengjiang sponge fossils.The main contents consists of the following aspects:(1)detailed description of 27 genera and 41 species,including 15 new genera and 23 new species;(2)restudy of Jiucunia and Saetaspongia,confirming their monaxons spicules identification;(3)report Haikouospongia lagenaria gen.et sp.nov.with three layers skeleton and diversified spicules;(4)report Alaspongia paradoxa gen.et sp.nov.with skeletons composed monaxons and spongin,indicating a basal position in demosponges,which is also supported by molecular data;(5)close examination of Paradiagoniella maga under scanning electron microscope(SEM)confirmed the existence of triaxonal,orthogonal hexactines,with trigonal cross-section of axial canal,suggesting that this animal is unlikely to be a crown taxa of hexactinelliid;(6)reported a complete sponge,Calliospongia chunchengia gen.et sp.nov.,with T-shaped megascleres;(7)use cladistics analysis methods to explore the phylogenetic relationships of Chengjiang hexactinelliids and demosponges,and Chengjiang sponges are divided into two major lineages of monaxons and triaxons;(8)15 new genera and 23 new species was established as follows:Crumillospongia orientalis sp.nov.,Paracrumillospongia spicata gen.et sp.nov.,Pseudotriticispongia monaxialis gen.et sp.nov.,Pseudosaetaspongia semipinnata gen.et sp.nov.,Pseudosaetaspongia brachyacantha gen.et sp.,Saetaspongia pubenti sp.nov.,Rigohirtella semireticulata gen.et.sp.nov.,Folispongia spinata gen.et sp.nov.,Stachyospongia longa gen.et sp.nov.,Yunnanospongia radialis gen.et sp.nov.,Polyramospongia bella gen.et sp.nov.,Halichondrites sclerospinea sp.nov.,Halichondrites chengjiangensis sp.nov.,Sentipongia clypealata gen.et sp.nov.,Ovulispongia multa gen.et.sp.nov.;Haikouospongia lagenaria gen.et sp.nov.,Paradiagoniella oliviformis sp.nov.,Paradiagoniella cylindrica sp.nov.,Paravalospongia bicornis gen.et sp.nov.,Stephenospongia chengjiangensis sp.nov.,Palaeoechidnina chengjiangia gen.et sp.nov.,Alaspongia paradoxa gen.et.sp.nov.,Calliospongia chunchengia gen.et sp.nov.