The existence of life, especially that of animals, before the Cambrian had long been the subject of debate in paleontology. The apparent suddenness of the Cambrian explosion had no firm explanation, and Charles Darwin himself recognized the challenge it posed for his theory of evolution. While reports of Precambrian organisms have been made since Alexander Murray's 1868 discovery of Aspidella, considerable evidence of Precambrian life had not been presented until the discovery of Charnia in 1956.
The period immediately preceding the Cambrian, the Ediacaran, is now widely accepted of containing animal life. It spans from 635 to 540 million years ago, and covers approximately 2% of Earth's history. Taxonomists have purported a total of 313 described genera from the Ediacaran, 207 of which are accepted as valid.
Key
Valid genus - Genera that are accepted by the scientific community Junior synonym - Alternative name for an already existing genus Unknown status - Unclear if it actually represents a unique organism Invalid - Genera that do not represent an actual fossil organism, or are taphonomic varieties of others
List