Science and Technology Daily News (reporter Zhang Ye Zhang Mengran) symmetry, sections, movement... These characteristics have become the "standard" for most modern animals. Figuring out when and how these iconic traits appear is important for studying the evolutionary history of animals.
On September 4, the journal Nature published a study by an early life research team at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, in which they found a strange fossil of a bug in the Ediacaran formation in the Three Gorges region, and its symmetrical segmental morphology and final tracks on both sides were preserved at the same time, and scientists named it Yiling worm. The discovery of Yiling insects suggests that 550 million years ago these features were simultaneously "assembled" on animals.
The symmetry and segmentation of the sides of the body are extremely important events in the evolutionary history of animals. The emergence of segments means that the structure of the body has been partitioned, and there is a division of labor in function. But when did such complex-sized animals emerge? It has been a focus of attention for paleontologists and evolutionary biologists.
In the "Cambrian Explosion", a large number of segmented symmetrical animals represented by trilobites appeared, and it is speculated that they should have had more ancient ancestors in the Ediacaran period before the Cambrian, but no reliable fossil evidence has been found.
In 2013, a team based on the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences discovered a specially preserved new type of animal fossil in the Slate Beach biota of the Ediacara Period Lantern Formation in the Three Gorges Region of Hubei Province, and the remains of the animal and the drag marks (imprints) of its last travel were preserved on a rock at the same time.
They spent nearly 5 years studying these fossils in detail. Its body is long striped, symmetrical on both sides, trifoliary-shaped, with obvious body segmentation, but also has a distinction between the front and back and abdomen. This is a completely new class of animal fossils, and no animals of the same form have been found in geological history and modern times, and researchers speculate that it may be link animals or arthropods. This suggests that in the Ediacaran period, there were already symmetrical epizoans with kinesthetic abilities and segments of the body.
The findings also show that benthic animals capable of free movement have emerged in the Ediacaran period and that seafloor sediments have been modified. It shows that the benthic ecosystem during the "Cambrian explosion" period has begun to build during this period, and gradually replaced the microbial base that ruled the earth for billions of years in the precambrian period, causing profound environmental and ecological impacts on the Earth's surface system.
![Don't dare to take revenge? Liu Beibing was defeated and died of depression, and Liu Chan did not have the courage to take the risk[fig]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)