NEW AND EXTRAORDINARY EARLY CAMBRIAN SPONGE SPICULE ASSEMBLAGE FROM CHINA

The fossil record of siliceous sponges, compared with that of other sk eleton-secreting Metazoa, is poorly known, based as it is on disarticu lated spicules and sporadically preserved body fossils. Abundant spicu les recovered from Lower Cambrian strata in Shaanxi, China, essentiall y double the known morphological diversity of siliceous sponges for th at interval of geologic time. These fossils, along with a comparable c oeval fauna from South Australia, have a remarkably modern aspect, the reby demonstrating that the principal siliceous sponge groups and styl es of body architecture were established quickly in the earliest Phane rozoic as part of the Cambrian ''explosion'' and that they inhabited a variety of low-energy, relatively deep water settings. The similarity of spicule shape and variation to that of younger assemblages reflect s a conservative architecture for the siliceous sponges.