Multicellular thallophytes with differentiated tissues from Late Proterozoic phosphate rocks of South China

Abstract

An assemblage of megascopic, multicellular thallophytes with well-preserved tissues and microstructures was discovered in phosphate rocks of the Late Proterozoic Doushantuo Formation (approximately 680 Ma old) at the Wengan-Fuquan Phosphate Mines, Guizhou Province, South China. Two new genera and three new species are erected: THALLOPHYCA ramosa n. gen. etn. sp. and WENGANIA globosa n. gen. et n. sp. The thalli of Thallophyca are embedded in amorphous collophane and consist of differentiated tissues interpreted as cortex and medulla, and distinct structures (conceptacle-like cavities and special cell-groups or ''cell-islands''). Tissue differentiation and megascopic (millimetric to centrimetric) size of the thalli suggest that the new genus Thallophyca may represent a primitive metaphyte. The new genus Wengania is assigned to the Paleozoic algal group Solenoporaceae Pia. This study provides reliable fossil evidence of Late Proterozoic metaphytes and leads to the following conclusions: (1) diverse multicellular thallophytes had evolved during Late Proterozoic Ediacaran time; (2) adaptive radiations possibly took place more or less contemporaneously in both metazoans and metaphytes, and (3) Precambrian phosphate rocks can preserve megafossils with delicate microstructures.