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The new hexactinellid stiodermatid Turgidaspongia porosa gen. et sp. nov. is described from the Ordovician-Silurian boundary sequence in Beigong of Jingxian County, south Anhui Province, China. The spherical, thin-walled species possessed unique features including unusually large parietal gaps on the body wall, swollen hexactines as hypodermalia, and two different sizes of stauractines as dermalia and parenchymalia respectively. Based on the new material, the family Stiodermatidae is revised here, including five genera after reassessment, i.e., Rigbyella, Thoracospongia, Stioderma, Uralonema, and Turgidaspongia porosa gen. et sp. nov. The new species is well preserved with typical enlarged hypodermal hexactines with swollen rays and large, subcircular parietal gaps, giving an illuminating insight into the affinity between the new species and other taxa in Stiodermatidae. It also provides a link between the Cambrian stiodermatid lineage and late Palaeozoic stiodermatid lineage. The uneven distribution of the swollen dermalia in the new species may relate to the sloughing of the dermal spicules causing by the nutrient deficiency. The unique rigid skeleton structure and unusually large parietal gaps probably represent new attempts on the skeletal evolution of hexactinellids in the Palaeozoic. [ABSTRACT FROM AUTHOR]

Seventeen trilobite species belonging to 16 genera and 13 families are systematically documented from the Houping Formation (upper Dapingian-lower Darriwilian, Middle Ordovician) at the Datangkou and Dacao sections, Chengkou, northern Chongqing. Of these, a new species, Mioptychopyge chengkouensis sp. nov., is established and described. New morphological information is provided for previously known species on the basis of new specimens. Two trilobite associations based on faunal composition and dominant forms are distinguished from the Houping Formation, in ascending order, the Agerina Association (from the lower and middle members) and the Nileus-Illaenus Association (from the upper member). The Agerina Association lived in an inner shelf margin environment with carbonate substrate above storm wave base (<70 m deep), whereas the Nileus-Illaenus Association developed in a shallow outer shelf environment below storm wave base (>70 m deep), indicating a rise of relative sea level corresponding to the early Darriwilian transgression. The cluster and nonmetric multidimensional scaling analyses of the trilobites in the formation show that the fauna had a strong endemicity to South China and a close biogeographic connection with east Peri-Gondwana, especially Tarim, Annamia and central Iran. [ABSTRACT FROM AUTHOR]