An early Ediacaran assemblage of macroscopic and morphologically differentiated eukaryotes

Area of Science:

• Paleontology
• Geology
• Biogeochemistry

Background:

• The Avalon biota (579-565 million years old) is considered the earliest complex macroscopic life.
• Its rise was hypothesized to be linked to Ediacaran deep-ocean oxygenation.

Observation:

• A diverse benthic macrofossil assemblage was discovered in Ediacaran Lantian Formation black shales in South China.
• These fossils are preserved in situ as carbonaceous compressions.

Findings:

• The Lantian biota is likely older and taxonomically distinct from the Avalon biota.
• This suggests early Ediacaran morphological diversification of macroscopic eukaryotes.
• It challenges the simple oxygenation model for early complex life.

Implications:

• Macroscopic eukaryotic diversification may have begun earlier in the Ediacaran Period, post-Marinoan glaciation.
• Ediacaran ocean redox history was more complex than previously assumed.
• Provides new insights into early life evolution and paleoenvironmental conditions.