Upper Ordovician cliefdenellids (Porifera: Sphinctozoa) from China

Aporate sphinctozoan sponges of the Family Cliefdenellidae Webby, 1969, are described for the Upper Ordovician (Ashgill) of northern and northwest China, including the new genus Khalfinaea and a new species K. shaanxiensis. They are characteristic cliefdenellids with conico-cylindrical and branching forms, a single central tube defined by a thickened, sieve-like endowall, and a filling of irregularly orientated astrorhizal canals, vesicles and thickened (?trabecular) tissue Taxonomic relationships of the other cliefdenellids are also discussed. The conception of the genus Cliefdenella Webby, 1969, is restricted to those forms with massive, hemispherical to explanate form and multiple, bundled vertical excurrent canal-clusters, and the new genus Rigbyetia is introduced to include conico-cylindrical and branching forms with a central tube composed of a single, vertical, bundled, excurrent canal-cluster In terms of their biogeographical record, the cliefdenellids have a restricted distribution in the Upper Ordovician (middle Caradoc-Ashgill) ‘fold-belt’ successions of the Palaeo-Pacific region (eastern Australia, Alaska and northern California) and in Asia (northern China, and in the Chinese and Soviet Altai).