Spectacular fossil treasure trove pushes back origins of complex animals
A newly discovered fossil site in southwest China has transformed our understanding of how complex animal life emerged on Earth, revealing that many key animal groups had already evolved before the start of the Cambrian Period. The study, led by researchers at Oxford University’s Museum of Natural History and Department of Earth Sciences as well as Yunnan University in China, has been published in Science.
3 Apr 2026
One of the most transformative events in Earth’s history was the rapid diversification of animal life, resulting in a dramatic increase in complexity and diversity from simpler life forms. Up to now, this was thought to have occurred at the start of the Cambrian Period, in an event known as the Cambrian explosion, starting around 535 million years ago. The new study, however, shifts this timeframe back by at least 4 million years, to the end of the Ediacaran period.
Lead author Dr Gaorong Li (Yunnan University at the time of the study, now Museum of Natural History, Oxford University), said: ‘Our discovery closes a major gap in the earliest phases of animal diversification. For the first time, we demonstrate that many complex animals, normally only found in the Cambrian, were present in the Ediacaran period, meaning that they evolved much earlier than previously demonstrated by fossil evidence.’
The discovery comes from the Jiangchuan Biota in Yunnan Province, southwest China, where more than 700 fossil specimens were recovered, aged between 554 and 539 million years old. The fossil site revealed a diverse community of Ediacaran organisms - both new, undescribed animal forms and groups known from the Cambrian period. Most strikingly, the international team identified fossils thought to be the oldest known relatives of deuterostomes – the broader group that today includes vertebrates such as humans and fish. The new fossils push the fossil record of deuterostomes back into the Ediacaran Period for the first time.
Among these fossil specimens were ancestors of modern starfish and their closest relatives, the acorn worms (the Ambulacraria*). These fossils have a U-shaped body and were attached to the seafloor with a stalk, with a pair of tentacles on their head used to catch food.
Co-author Dr Frankie Dunn (Museum of Natural History, Oxford University) said: ‘The presence of these ambulacrarians in the Ediacaran period is really exciting. We have already found fossils which are distant relatives of starfish and sea cucumbers and are looking for more. The discovery of ambulacrarian fossils in the Jiangchuan biota also means that the chordates – animals with a backbone – must also have existed at this time.’
https://www.ox.ac.uk/news/2026-04-03-sp ... ex-animals
Left: Haootia-like fossil (an early cnidarian – the phylum that includes jellyfish, sea anemones and corals) from the Jiangchuan Biota (scale bar: 2 mm) and artist’s reconstruction. Right: A deuterostome cambroernid fossil from the Jiangchuan Biota (scale bar: 2mm) and artist’s reconstruction. Credits: Gaorong Li (fossil photographs) and Xiaodong Wang (artistic reconstruction).
