Almost 600 million years ago, before the rapid evolution of life forms known as the Cambrian explosion, a community of seaweeds and worm-like animals lived in a quiet deep-water niche near what is now Lantian, a small village in south China.
Then they simply died, leaving some 3,000 nearly pristine fossils preserved between beds of black shale deposited in oxygen-free and unbreathable waters.
Scientists from the Chinese Academy of Sciences, Virginia Tech in the United States and Northwest University in Xi'an, China report the discovery of the fossils in the Feb. 17 issue of the journal Nature.
In addition to ancient versions of algae and worms, the Lantian biota--named for its location--included macrofossils with complex and puzzling structures.
In all, scientists have identified some 15 species at the site.
The fossils suggest that structural diversification of macroscopic eukaryotes--the earliest versions of organisms with complex cell structures--may have occurred only tens of millions of years after the Snowball Earth event that ended 635 million years ago.
Snowball Earth proposes that the Earth's surface became almost, or completely, frozen at least once during the planet's history.
The presence of macroscopic eukaryotes in the highly organic-rich black shale suggests that, despite the overall oxygen-free conditions, brief oxygenation of the oceans did come and go, according to H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.
"So there are two questions," says Shuhai Xiao, a geobiologist at Virginia Tech. "Why did this community evolve when, and where, it did?
"It is clearly different in terms of the number of species compared to biota preserved in older rocks. There are more species here, and they are more complex and larger than what evolved before."
The rocks were formed s
|Contact: Cheryl Dybas|
National Science Foundation