Permineralized Fossils from the Terminal Proterozoic Doushantuo Formation, South China

Abstract

Permineralized fossils of the terminal Proterozoic (600–550 Ma) Doushantuo 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 preserve prokaryotes and protists from subtidal marine environments below and 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 Formation, 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. Thirty-one species of spheromorphic and acanthomorphic acritarchs are recognized, about half of which occur elsewhere in rocks of the same approximate 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 diversity 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 shales from the top of the formation, Doushantuo permineralizations indicate that large animals radiated into a world rich in prokaryotic, protistan, and, even, multicellular diversity.