Xiaodong Wang
Artistic reconstruction of the Jiangchuan biota.
It will be the first fossil evidence that many complex animals, until now considered typical of the Cambrian, already existed in the Ediacaran. Biota in China will be a transitional community between two fundamental moments in the history of life.
Several major animal groups arose millions of years earlier than science previously thought, according to a new study April 2 in Science.
The conclusion is based on a fossil discovery in China, considered remarkable for anticipating the diversification that for decades was associated almost exclusively with the so-called “Cambrian explosion”.
The new finds, with more than 540 million yearsindicate that the evolutionary transformation that gave rise to more complex animals was already underway at the end of the Ediacaran period, at least four million years before the beginning of the Cambrian, traditionally dated to around 535 million years ago.
At the heart of this discovery is the biota de Jiangchuanin the Chinese province of Yunnan, where scientists have collected more than 700 fossils aged between 554 and 539 million years. The collection reveals a surprisingly diverse ecosystem, with organisms that include primitive relatives of sea starsanimals vermiforms with bilateral symmetry and even ancestral forms linked to the lineage of deuterostomies — the large group that includes vertebrates, such as fish and humans.
This will be the first time that there is clear fossil evidence that many complex animals, until now considered typical of the Cambrian, already existed in the Ediacaran. The discovery “closes a big gap” in the early stages of animal diversification, admits the main researcher, Gaorong Li, cited by .
Among the most important fossils are specimens interpreted as the oldest known relatives of deuterostomes. The presence of these organisms pushes the fossil record of this group back to the Ediacaran for the first time. Researchers also found primitive representatives of outpatient clinicsa group that includes sea stars and their close relatives such as acorn worms. These animals had U-shaped bodies, attachment to the seabed by a peduncle and tentacles close to the head, probably used to capture food.
The team also highlights the presence of bilaterian worm-like organismssome with complex feeding strategies, as well as rare fossils that may correspond to early forms of ctenophoresor comb jellies.
Many of the specimens display unusual anatomical combinations — tentacles, attachment discs, reversible food structures and peduncles — that do not coincide with any known species, neither from the Ediacaran nor the Cambrian.
This mix of characteristics reinforces the idea that Jiangchuan has a transition community between two fundamental moments in the history of life.
The ecosystem can help solve an old problem in evolutionary biology. Genetic studies and fossil remains have suggested for years that several animal lineages must have existed before the Cambrian explosion, but direct and robust fossil evidence was lacking. And unlike most Ediacaran sites, where organisms appear as simple impressions in sandstone, the Jiangchuan fossils were preserved in the form of carbonaceous films — a type of preservation that allows you to observe fine details of anatomy, including feeding structures, digestive systems, and organs associated with movement.
