Researchers have found over 700 fossil specimens at the Jiangchuan Biota site in Yunnan Province. The fossils are preserved as thin carbon films, allowing inner structures to be discerned. They provide the first direct link between trace fossils in the seafloor and actual animal bodies from that era. According to the lead author, the discovery closes a major gap in the earliest phases of animal diversification and demonstrates that many complex animals were present in the Ediacaran period, meaning they evolved much earlier than previously shown by fossil evidence.
The fossils include the oldest known relatives of deuterostomes, the group that includes vertebrates like humans and fish. They also include ancestors of starfish and acorn worms (Ambulacraria). According to a co-author, the presence of these ambulacrarians in the Ediacaran period is really exciting. The fossils help resolve the 'rocks versus clocks' debate by providing fossil evidence that matches genetic analysis predictions for early animal evolution. However, it remains unknown what specific new animal species or genera have been identified from the over 700 fossils, and how exactly these fossils change the timeline for the evolution of chordates (animals with backbones).
The research was led by scientists from Oxford University and Yunnan University. The study was published in the journal Science. The discovery site is near a UNESCO Chengjiang world natural heritage site in Yunnan Province. According to a researcher, among animals today, we have an enormous diversity, and most of that diversity actually comes from animals that have a bilateral body, just like us. According to another researcher, such fossils are time capsules, a moment from an animal's life hundreds of millions of years ago, and the only way for us to reach that really deep history.
According to a researcher, this is the first window we have into how basically the modern animal-dominated biosphere was formed and developed and came through this weird Ediacaran transitional interlude. According to another researcher, now we know what's making them because we have those fossils for the first time. According to a researcher, if we see the Cambrian as a period with a rich animal life, perhaps one wants to move that boundary back a bit. The environmental conditions that allowed such detailed preservation of these fossils as carbon films are not yet clear, and it is unknown how this discovery will impact the formal geological definition of the Cambrian period boundary or what implications it has for understanding the causes of the Cambrian explosion.