A groundbreaking fossil discovery in China's Yunnan province reveals that complex animals, including potential ancestors of vertebrates, existed at least 4 million years earlier than previously thought, during the late Ediacaran period.
Discovery at Jiangchuan Biota
- Located in Yunnan province, the Jiangchuan Biota site spans about 50 square meters.
- Fossils date to the late Ediacaran period, approximately 554-539 million years ago.
- Researchers excavated around 700 specimens between 2022 and 2025, with about 200 representing animals, many under 2.5 centimeters long.
- Key fossils include:
- Goblet-shaped sea jelly relatives resembling Haootia quadriformis.
- Sausage-shaped worms with flat "holdfast" discs for anchoring.
- Creatures similar to Herpetogaster, previously known only from the Cambrian.
Exceptional Preservation Details
- Fossils preserved as biofilm through rapid burial and compression between rock layers.
- Two-dimensional impressions retain soft tissues, feeding structures, delicate limbs, and traces of internal organs.
- This represents the first highly detailed Ediacaran fossils with Cambrian-like preservation quality.
Blurring Ediacaran and Cambrian Boundaries
- The site shows a mix of Ediacaran-style and Cambrian-style organisms in a single locality.
- Many fossils exhibit bilateral symmetry, a trait common in modern animals, indicating its evolution before the Cambrian.
- A sausage-shaped worm preserves a visible gut, rare for Ediacaran fossils which typically only show body impressions.
- Some fossils potentially represent deuterostomes, the group including vertebrates, starfish, and sea urchins.
Evolutionary and Scientific Implications
- Complex animal life, possibly including deuterostome ancestors, arose between 554-539 million years ago, at least 4 million years before the Cambrian.
- Supports growing evidence that the Cambrian explosion's evolutionary boom may have started in the Ediacaran.
- However, the Cambrian period remains unique for the emergence of new animal phyla like mollusks and arthropods.
Challenges and Future Research
- Classifying these extinct animals is challenging due to limited fossil characters and lack of preserved DNA.
- Scientists will investigate the site's preservation conditions and the animals' ecologies, habits, and interactions.
- Research aims to deepen understanding of early animal evolution and human ancestry.
Source: Study published in Science, with contributions from international researchers.
