The Ediacaran fauna were an enigmatic population of organisms that lived prior to the Cambrian explosion, when the evolution of hard shells made fossilization easier. Fossils from the Ediacaran era range in age between 542 and 635 million years, but are often found damaged by the distortion of their rocks.
What little is known about Edicaran fauna comes mainly from three sites where the fossils have been found. Distortion of the ancient rocks notwithstanding, the specimens themselves are difficult to interpret. Some of the preserved animals are recognizable as ancestors of modern arthropods and cnidarians, while others cannot reliably be classed with any modern animal. Sometimes it cannot be determined to which kingdom of life the specimens belonged.