Potential Ediacaran sponge gemmules from the Yangtze Gorges area in South China

• Subspherical siliceous microfossils are described from the Neoproterozoic dolostones, South China.
• They strongly resemble sponge gemmules and associated gemmoscleres.
• They would be the oldest gemmule fossils, and the oldest evidence for metazoan silica biomineralization.

Sponges are widely viewed as the most primitive metazoans. Sponge gemmule-like structures have been recovered from the lower part of the Doushantuo Formation in the Yangtze Gorges area (South China), that were deposited between 635 and 580 Ma. Gemmosclere-like structures are embedded in the outer coat of the sponge structures. Electron probe microanalyses (EPMA) of the gemmoscleresindicate that they have siliceous composition. The naked subspheroidal sponge structures are composed of three layers, consistent with the preservation of a tri-layered theca embedded with the gemmosclere-like structures. The potential fossils of the Ediacaran sponge gemmules in the Doushantuo Formation may provide one of the earliest records of sponges.

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