http://www.newsweek.com/ancient-footprints-fossils-bugs-963761

Scientists think they have discovered the 550-million-year-old footprints of a small bug-like animal in the Yangtze Gorges area of China. This critter was roaming the planet millions of years before the first mammals, the first dinosaurs, and even the first fish.

Created before the Cambrian Explosion—a sudden burst in animal diversity that took place about 541 million years ago—scientists think these are the oldest trackways ever discovered on Earth. They published their findings Wednesday in the journal Science Advances.