Newly identified fossil remains in southwestern China are changing scientists’ understanding of how complex animal life first developed on Earth. The discovery shows that many major animal groups already existed before the Cambrian period began. The research was led by a team from Oxford University’s Natural History Museum and School of Earth Sciences, Yunnan University in China, and was published in the journal April 2. science.
Scientists have long believed that a rapid increase in diverse and complex animals, known as the Cambrian Explosion, began about 535 million years ago. This period marked a dramatic change from simple organisms to a variety of more advanced life forms. New research shows that this change began at least 4 million years ago, during the late Ediacaran period.
Lead author Dr Gaorong Li, originally from Yunnan University and now at Oxford University’s Natural History Museum, said: “Our discovery fills a major gap in the early stages of animal diversification. We demonstrate for the first time that many complex animals normally found only in the Cambrian were present during the Ediacaran period. This means they evolved much earlier than previously proven by fossil evidence.”
Fossils from the Egawa biota show early animal diversity
The fossils were discovered in the Jiangchuan biota in Yunnan province, where researchers collected more than 700 specimens dating from 554 to 539 million years ago. The site reveals a rich and diverse Ediacaran ecosystem, including previously unknown species and animals thought to have only appeared in the Late Cambrian.
Among the most important discoveries are fossils believed to be the oldest known relatives of deuterostomes, a major group that includes humans and vertebrates such as fish. These discoveries extend the fossil record of this group back to Ediacaran times for the first time.
The collection also includes early relatives of starfish and their close relatives, the acorn worms (Ambulacraria(2)). These creatures had U-shaped bodies and were anchored to the ocean floor by stems. Tentacles near the head were probably used to capture food.
Co-author Dr Frankie Dunn (Natural History Museum, Oxford University) said: “The presence of these amphicephalans in the Ediacaran period is really interesting. Fossils of distant relatives of starfish and sea cucumbers have already been found, and we are looking for more. The discovery of amphocephalic fossils in the Egawa biota also means that chordates (animals with backbones) must also have existed at this time.” It’s time. ”
Strange creatures and transitional ecosystems
Other fossils include worm-like bilateral animals (with bilateral symmetry) that exhibit complex feeding strategies, as well as rare specimens thought to represent early comb jellyfish.
Many of the fossils display unusual combinations of features, including tentacles, stalks, attachment discs, and everting feeding structures. These combinations do not match any known species from the Ediacaran or Cambrian periods. “For example, one specimen looks a lot like the Sandworm from Dune!” Dr. Dunn added.
Co-author Associate Professor Luke Parry, from the University of Oxford’s School of Earth Sciences, added: “This discovery is very exciting as it reveals a transitional community. The strange world of the Ediacaran period gave way to the Cambrian period, the next period when animals living today are much easier to classify into groups. When we first saw these specimens, it was clear that this was something completely unique and unexpected.”
Solving the long-standing mystery of evolution
The discovery helps answer a long-standing question in evolutionary biology. Previous genetic studies and fossil traces suggested that many animal lineages existed before the Cambrian explosion. However, clear fossil evidence from this early period has been largely lost until now.
Good preservation reveals hidden details
Unlike most Ediacaran fossil sites, which preserve organisms as simple traces in sandstone, the Egawa biota fossils are preserved as carbonaceous membranes. This type of preservation is more commonly associated with famous Cambrian fossil sites such as the Burgess Shale in Canada. This allows scientists to observe details such as feeding structures, digestive systems, and organs related to locomotion.
Co-author Associate Professor Ross Anderson (Natural History Museum, Oxford University) said: “Our findings indicate that the apparent absence of these complex fauna at other Ediacaran sites may reflect differences in preservation, rather than a true biological absence. Carbonaceous compactions such as those at Egawa are rare in rocks of this age, which means that similar assemblages may not be preserved elsewhere.”
Years of fieldwork lead to groundbreaking discoveries
The fossil was discovered by a Yunnan University research team led by Professor Peiyun Cong and Associate Professor Fan Wei. The group spent nearly 10 years searching for fossils of a variety of Ediacaran animals. Fossils had previously been found in eastern Yunnan province, but they were limited to algae and did not contain animal remains.
“After many years of fieldwork, we have finally discovered several sites with suitable conditions where animal fossils are preserved along with rich algae,” said Associate Professor Huang.
“The new fossils provide the most convincing evidence of the existence of diverse bilateral animals at the end of the Ediacaran period, evidence that people have been looking for for decades,” said Professor Feng Tang of the Chinese Academy of Geological Sciences in Beijing, whose previous work guided the study.
Precautions
- It’s pronounced “jinchoan”.
- Umbracularia comes from the Latin word ambraculum, meaning “wooded promenade.”
