Among a heap of recently unearthed microscopic fossils dating to around 1 billion years ago are the preserved organic bodies of lake-dwelling eukaryotes that may have lived, at least part of the time, above the surface of the water.
This "ball of cells" is about 30 micrometers in
diameter and represents a level of complexity that
was previously unknown in organisms thought to
inhabit freshwater settings a billion years ago.

Image: Courtesy of Paul Strother
The finding, published this week in __Nature__, not only suggests that freshwater environments at this time rivaled the oceans as significant hotspots of eukaryotic evolution, but also provides compelling evidence that eukaryotes may have adapted to life on land nearly 500 million years earlier than the current fossil record suggests."This is very exciting," said paleontologist linkurl:Susannah Porter,; who did not participate in the research. "Going back around 2.5 billion years ago, we probably had bacterial...
This tri-lobed thallus or "black blob" has a
morphology that is mimicking a morphology that
exists today in certain kinds of plants.

Image: Courtesy of Paul Strother
P.K. Strother et al., "Earth's earliest non-marine eukaryotes," Nature, doi:10.1038/nature09943, 2011.Correction (April 13): The original version of this story incorrectly quoted Susannah Porter as saying that there were bacterial mats on land 2.5 million ago. The date was corrected to 2.5 billion years ago. The Scientist regrets the error.

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