About 600 million years ago, when Earth was a little lonely (the Cambrian explosion of diverse life forms hadn't happened yet), the village of Lantian in central China was covered by an oxygenless ocean. The anoxic Lantian Basin would have been especially lonely, mostly unable to support large, complex, multicellular organisms that require oxygen for respiration.

But for brief periods, the water in the basin did hold oxygen, a team of U.S. and Chinese scientists now proposes in a paper published on February 16 in Nature. (Scientific American is part of Nature Publishing Group.) In those oxygenated flashes of time seaweeds and what may be algae or worms took hold. They died again when the oxygen dissipated, leaving behind more than 3,000 well-preserved fossils, such as this one preserving a three-centimeter-long seaweed. These are the oldest fossils of large seaweeds ever found, according to a prepared statement from the National Science Foundation, which partially funded the study. The excavating team identified 15 species of life recorded in the fossils.

—Francie Diep