Study On The Systematic Classification And Trophic Structure (Tiering) Of Sponges In The Palang Formation Of The Cambrian (Second Series) In Jianhe, Guizho

Sponges,as one of the most primitive animals,are crucially important to explore the origin and early evolution of the metazoan.Sponges are one of the largest groups of benthic marine communities,and flourish in not only the modern world but also the Cambrian Period.Thus,they have been used to explore the relationship between Cambrian animals and marine ecological environment.Many well-preserved sponge fossils have been discovered from the Cambrian(Stage 4)Balang Formation of East Guizhou,and a comprehensive classification of these sponge fossils has been conducted based on their morphological and spicule characters.The sponge assemblage includes 10 genera with 11 species: Leptomitus teretiusculus,Leptomitus cf.L.teretiusculus,Paraleptomitella dictyodroma,Choia cf.C.carteri,Choiaella radiata,Lenica jianhensis sp.nov.,Lenica cf.L.unica,Saetaspongia cf.S.densa,Solactiniella cf.S.plumata,Hyalocinica archaica,and Hyalosinica jianhensis sp.nov.By combining information from previous studies and the present research,the characteristics of the Cambrian sponge communities and their biogeography have been discussed.The results suggest that the Balang sponge community is dominated by protomonaxonids,and include one endemic genus(Jiahella)and 6 cosmopolitan genera(Leptomitus,Saetaspongia,Solactiniella,Lenica,Choia,Hamptonia).And then the phylogenetic relationships of leptomitids,choiids,halichondritids,Saetaspongia and Hyalocinica are discussed,suggesting that Saetaspongia has a close affinity with some ancestral members of leptomitids.Besides,the results further support the conclusions that Paraleptomitella may represent an intermediate form between leptomitids and basal protomonaxonids,the Jianhella was probably derived from a deep division within earlier leptomitid sponges,Leptomitus was derived from the latter protomonaxonids,the Choia was derived from the related groups of Choiaella,the Lenica had a close affinity with the Choia,and the Hyalocinica represented a basal protomonaxonid.To study the tiering of Cambrian sponges and discusses their paleoecology,the tiering and paleoecology of the Balang sponge community are explored based on their skeletal and spicule characters.The research shows that the Balang sponge community had a well-developed two-level tiering,consisting of 0-5 cm and 5-15 cm tiers;and their lifestyles were mostly sediment sticker(i.e.,they inserted into the deeper substrates via their root tuft spicules).The tiering of the sponge community is related to the environment,spicule complexity and lifestyles,showing that the sponges feeding in the higher tiering levels have a more complex skeleton(e.g.,Hyalocinica,Jianhella).These sponges have a wide range in the vertical space,and they tend to be only sediment stickers.On the contrary,the sponges feeding in the lower tiering levels don’t have a complicated skeleton(e.g.,Leptomitus,Paraleptomitella,Saetaspongia,Solactinella,Choia,Choiaella,Hamptonia,Lenica),and thus they have a narrow range in the vertical space.These sponges tend to be sediment sticker or rester.