CAMBRIAN SPONGE ASSEMBLAGES FROM GUIZHOU

Abstract

Cambrian sponges from Guizhou are abundant, and have been founded mostly in the lower Cambrian Gezhongwu Formation in Zhijin, the Niutitang Formation in Zunyi, Jinsha, Danzhai and lower-middle Cambrian Kaili Formation in Taijiang. Sponge body fossil Triticispongia sp. and mass sponge spicules which first occur in Meishucunian, may be forerunners of the sponges before rapid radiation during Qiongzhusian. Sponges in the Niutitang Formation are abundant not only in numbers but also in bodyforms, 13 sponge genera constitute 70% of the whole biota, so the Niutitang Formation is a window of the first sponge radiation. These sponges are similar to that of the lower Cambrian Chengjiang biota rather than those of the Niutitang Formation at Sancha, Dayong, Hunan Province because they are mostly Demospongea, whereas in the Niutitang Formation at Sancha are primarily Hexactinellida. There are re- latively few sponges in the middle Cambrian Kaili Biota, only 7 genera, and make up 6 percent of the biota. Demospongea are dominant in the Kaili biota. It is shown that the radiation of the Demospongea took place in the Qiongzhusian. Comparison of the Cambrian sponge assemblages indicates that compositions of sponge assemblages are controlled by environments. Discoveries and studies of Cambrian sponges from Guizhou provide new information for understanding early history of sponge evolution and diversity of the Cambrian marine animals.