An early Ediacaran assemblage of macroscopic and morphologically differentiated eukaryotes

Abstract

The deep-water Avalon biota (about 579 to 565 million years old) is often regarded as the earliest-known fossil assemblage with macroscopic and morphologically complex life forms. It has been proposed that the rise of the Avalon biota was triggered by the oxygenation of mid-Ediacaran deep oceans. Here we report a diverse assemblage of morphologically differentiated benthic macrofossils that were preserved largely in situ as carbonaceous compressions in black shales of the Ediacaran Lantian Formation (southern Anhui Province, South China). The Lantian biota, probably older than and taxonomically distinct from the Avalon biota, suggests that morphological diversification of macroscopic eukaryotes may have occurred in the early Ediacaran Period, perhaps shortly after the Marinoan glaciation, and that the redox history of Ediacaran oceans was more complex than previously thought.

Rare earth elements and carbon isotope geochemistry of the Doushantuo Formation in South China: Implication for middle Ediacaran shallow marine redox conditions

“…Fe speciation data from well-preserved Neoproterozoic sedimentary rocks suggest an anoxic ferruginous condition as a general feature of deep oceans between 750 and 540 Ma [31]. Fe speciation data of the Ediacaran-early Cambrian sedimentary rocks (Doushantuo, Liuchapo, and Niutitang formations) deposited in outer shelf to basinal environment in South China suggest an anoxic condition in deep oceans [31][32][33], although paleontological data indicate that the largely anoxic basin may be punctuated by brief oxic episodes [34,35].…”

The Lantian biota: A new window onto the origin and early evolution of multicellular organisms

“…According to the new data [50], the Lantian biota represents one of the oldest biotas with diverse assemblage of complex multicellular macro-eukaryotes, as well as intriguing fossils with possible hints of animal affinities.…”

“…According to chemostratigraphic, sequence stratigraphic and event stratigraphic data, combined with regional stratigraphic correlation, the Lantian biota is probably older than the Ediacara biota, with an age between 580 and 635 Ma [50]. Lantian fossils are preserved as carbonaceous compressions on bedding surfaces of black shales ( Figure 1).…”

“…Shortly after the end of the Marinoan glaciations, the Lantian biota evolved. This implies that sufficient oxygen must have been locally and intermittently available in the Lantian basin to support macroscopic organisms [50]. However, the Lantian basin was probably predominately anoxic [38], which may have facilitated the in-situ fossil preservation.…”

Geochemical constraints on the origin of Doushantuo cap carbonates in the Yangtze Gorges area, South China

“…Most Marinoan glacial deposits are directly overlain by "cap carbonates" with peculiar sedimentary features and negative carbon isotope signatures (Kennedy, 1996;Hoffman et al, 1998;James et al, 2001;Hoffman and Schrag, 2002;Jiang et al, 2003a;Frimmel and Folling, 2004;Shields et al, 2007a, b;Zhou and Xiao, 2007;Shen et al, 2008), implying severe and rapid climatic changes which are thought to serve as an 'environmental filter' for biological evolution (Hoffman et al, 1998;Runnegar, 2000;Hoffman and Schrag, 2002). Strata above these postglacial cap carbonates contain the Earth's earliest multi-cellular organisms interpreted as early Metazoans (Xiao et al, 2002;Xiao, 2004;Yin et al, 2007;McFadden et al, 2008;Yuan et al, 2011). These cap carbonates have been of special interest, understandably, as they may provide significant hints about the link between the earliest diversification of animals and the most severe glaciation in Earth's history.…”