PERMINERALIZED FOSSILS FROM THE TERMINAL PROTEROZOIC DOUSHANTUO FORMATION, SOUTH CHINA

Permineralized fossils of the terminal Proterozoic (600-550 Ma) Dousha ntuo Formation, China, provide an unusually clear window on biological diversity just before the Ediacaran radiation. In the eastern Yangtze Gorges region, cherts in lower and upper Doushantuo carbonates preser ve prokaryotes and protists from subtidal marine environments below an d above fair weather wave base, respectively. Phosphorites in the Weng 'an district to the south contain diverse acanthomorphic acritarchs as well as cellularly preserved thalloid algae. Twelve taxa of probable cyanobacteria are recognized. None is endemic to the Doushantuo Format ion, and most have long stratigraphic ranges. The apparent restriction of two species to late Neoproterozoic and Cambrian rocks may reflect secular variation in taphonomic circumstance rather than evolution. Th irty-one species of spheromorphic and acanthomorphic acritarchs are re cognized, about half of which occur elsewhere in rocks of the same app roximate age. At least some of the eight formally described species of multicellular algae can be assigned with confidence to the Rhodophyta ; these fossils provide a glimpse of structural and reproductive diver sity in Neoproterozoic algae that is, to date, unique. Several reports of Doushantuo animal fossils have been published; most compelling are triact spicules identified in chert nodules. Along with more than two dozen taxa of compressed macrofossils preserved in carbonaceous shale s from the top of the formation, Doushantuo permineralizations indicat e that large animals radiated into a world rich in prokaryotic, protis tan, and, even, multicellular diversity.