Eumetazoan fossils in terminal proterozoic phosphorites?

Area of Science:

• Paleontology
• Sedimentary Geology
• Early Life Evolution

Background:

• Phosphatic sedimentary rocks offer a distinct fossil record complementary to Ediacaran fossils.
• The Doushantuo Formation phosphorites contain microfossils potentially representing early animal life stages.

Purpose of the Study:

• To analyze microfossils from the Doushantuo Formation phosphorites.
• To investigate the phylogenetic position and taphonomic history of early animal life.

Main Methods:

• Microfossil analysis of Doushantuo Formation phosphorites.
• Comparative analysis with Ediacaran fossils and known diagenetic processes.

Main Results:

• Fossils include eggs, egg cases, and stereoblastulae of uncertain phylogenetic origin.
• Putative sponge spicules and millimeter-scale tubes resembling extinct cnidarians (tabulates) were identified.
• Microfossil interpretations as cnidarian/bilaterian gastrulae are challenged by diagenetic alterations; alternative interpretations as algal cysts are proposed.

Conclusions:

• Doushantuo phosphorites provide evidence for early eumetazoans, particularly cnidarians, through tubular fossils.
• These fossils may represent stem-group eumetazoans or cnidarians from the late Proterozoic.
• The study highlights the importance of phosphatic rocks in understanding early animal evolution.