Single-Celled Giant (3cm) Upends Early Evolution

"Slowly rolling across the ocean floor, a humble single-celled creature is poised to revolutionize our understanding of how complex life evolved on Earth. [...] The trouble is, single-celled critters aren't supposed to be able to leave trails. The oldest fossils of animal trails, called 'trace fossils', date to around 580 million years ago, and paleontologists always figured they must have been made by multicellular animals with complex, symmetrical bodies. [...] At up to three centimeters (1.2 inches) in diameter, they're also enormous compared to most of their microscopic cousins. "If these guys were alive 600 million years ago, and their traces got fossilized, a paleontologist who had never seen this thing would not have a shade of doubt attributing this kind of trace to the activity of a big, multicellular, bilaterally symmetrical animal," Matz said."~Discovery.com