Scientists from the Chinese Academy of Sciences’ Nanjing Institute of Geology and Palaeontology and Virginia Tech (the United States) have found a fossilized trail of the animal Yilingia spiciformis, dating back 550 million years. The researchers discovered 35 fossils in the Yangtze Gorges area. The creature had a bilaterally symmetrical body consisting of 50 segments. It was no more than 2.6cm wide and about 27cm long.
The finding confirms that mobile and segmented bilateral animals existed in the Ediacaran Period (between 635 and 539 million years ago). Previously, scientists could only assume the existence of mobile animals during that period, because there were no fossils. The reason for their absence, according to paleontologists, is that the organisms did not have crusts back then, and they quickly decomposed after death.
The newly-discovered creature belongs to a group of bilaterally symmetrical animals (Bilateria) that includes 99 percent of organisms. There is a hypothesis that all of them came from a common ancestor that lived on the planet between 600 and 500 million years ago.