Tetraradial symmetry in early poriferans  

作　　者：Joseph P.Botting Xunlai Yuan Jih Pai Lin 

机构地区：[1]State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences

出　　处：《Chinese Science Bulletin》2014年第7期639-644,共6页

基　　金：supported by the Chinese Academy ofSciences(KZZD-EW-02);the Project-Oriented Hundred TalentsProgram of the Chinese Academy of Sciences(KZCX2-YW-BR-23);the National Science Foundation of China Research Fellowshipfor International Young Scientists(41150110152)

摘　　要：Here is currently little consensus on the branching order and phyletic status of the oldest metazoan groups, but sponges are widely believed to be the earliestbranching living metazoans. Porifera are thought to have diverged before the emergence of developmental characters typical of Eumetazoa, such as well-defined symmetry; extant sponges show radial symmetry of indeterminate high order, or none, combined with polarisation along the axis. In contrast, other early-branching phyla include bilateral and tetraradial(Cnidaria) and biradial(Ctenophora) symmetry, or none(Placozoa). A variety of prismatic early fossil sponges had shown here where the shared symmetry has been overlooked, and also describe structural tetraradial symmetry in Cambrian sponges from South China. Based on this study, this symmetry is likely to have been a primitive feature of sponges, and that the earliest-known fossil sponges were highly organised, cellularly integrated individuals whose body form was under strict genetic control.Here is currently little consensus on the branching order and phyletic status of the oldest metazoan groups, but sponges are widely believed to be the earliest- branching living metazoans. Porifera are thought to have diverged before the emergence of developmental charac- ters typical of Eumetazoa, such as well-defined symmetry; extant sponges show radial symmetry of indeterminate high order, or none, combined with polarisation along the axis. In contrast, other early-branching phyla include bilateral and tetraradial （Cnidaria） and biradial （Cte- nophora） symmetry, or none （Placozoa）. A variety of prismatic early fossil sponges had shown here where the shared symmetry has been overlooked, and also describe structural tetraradial symmetry in Cambrian sponges from South China. Based on this study, this symmetry is likely to have been a primitive feature of sponges, and that the earliest-known fossil sponges were highly organised, cel- lularly integrated individuals whose body form was under strict genetic control.

关 键 词：对称性 早期 后生动物群 多细胞动物 多孔动物 中国南方 原始特征 遗传控制 

分 类 号：Q915[天文地球—古生物学与地层学]