Source: Science and Technology Daily
Original title: China found the oldest known footprint fossil
Who left footprints from 500 million years ago? A paper published on June 6, US time, a sub-journal of Science, unveiled the mystery: Chinese and American scientists found the oldest footprint fossils on earth in the Ediacaran formation of the Three Gorges, and speculated that the footprints left were likely to be arthropods, link animals or their ancestors.
Symmetrical animals with appendages (wart feet), such as arthropods and link animals, are the most abundant and diverse animal phyla in the present and geological history periods. When they appear has always been a concern for biologists and paleontologists. Although it is speculated that their ancestors may have appeared in the Ediacaran period between 635 million and 541 million years ago, no definitive fossil evidence has been found in the Ediacaran formation. As a result, symmetrical epizoans with appendages are widely believed to have appeared only suddenly during the Cambrian explosion of life, about 541 million to 510 million years ago.
A series of footprint fossils found in the Edikara Formation (551 million to 541 million years ago) in the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences and Virginia Tech University of the United States in the Ediacara Formation (551 million to 541 million years ago) in the Three Gorges region of Yichang, Hubei Province, provide important clues to the origin of symmetrical animals with appendages on both sides. The discovery advances the record of fossil footprints to the Ediacaran period, the oldest known footprint.
The fossil footprints found this time consist of two columns of footprints that form repeating "sequences" or "clusters." Although slightly irregular, these footprints exhibit features that reflect the fact that trace organisms (organisms that can form relics) can support their bodies from the surface of the sediment through their appendages. The remains are clearly formed by symmetrical epizoa on both sides, and these epizoa have paired appendages. At the same time, these footprint fossils are connected to the submerged cavity, reflecting the complexity of the behavior of the trace organisms — they sometimes burrow under the algae mat layer for feeding and oxygen, and sometimes drill out the algae mat layer to crawl on the surface of the sediment. (Reporter Zhang Ye)