在中国西南云南的江川生物群（Jiangchuan Biota）中，研究者检视了超过 700 件化石，结果显示主要动物多样化与演化复杂化比先前认知更早。这批化石年代超过 500 兆? years（>500 Ma，约5.0×10^8 年）且与寒武纪开始前的 539 Ma 分界相比，表明关键演化增长可能已在该界线之前就已启动。该群化石将晚期 Ediacaran 生态群与早期 Cambrian 生物群衔接起来，将所谓 Cambrian explosion 的开始推进至 Ediacaran 末期。

由 Luke Parry、Frankie Dunn 与英国及中国团队合作研究，包含了既往已报导与新鉴定的类群；其中有被视为目前已知最古老 deuterostomes 的标本。文中部分标本被解读为 acorn worms，这类生物可在U字形掘穴中活动，并以头部成对触手捕食。这一化石证据与先前来自生物采样与 traces 的分子推估一致，支持 deuterostomes 在 Cambrian 之前已出现，因此与之并列的 chordates（含脊椎动物谱系）也应同时存在于此时段。

这项研究也凸显了 bilateral symmetry（双侧对称）作为重要演化机制的作用。与水母等辐射对称生物不同，双侧对称有利于朝向性运动与感官集中，例如头部主要感觉器官的形成、一条具有口与肛门的单向消化道，以及逐步复杂化的肌肉与神经系统。Imran Rahman 指出，该 assemblage 弥补了最早 deuterostome 化石证据与分子时间估计之间的缺口，支持是 Ediacaran 向 Cambrian 的过渡，而非仅在 539 Ma 时突然展开的突变。

A fossil assemblage from the Jiangchuan Biota in Yunnan, southwest China (more than 700 specimens) shows that major animal diversification and complexity likely began earlier than previously thought. The material is more than 500 million years old, and relative to the Cambrian boundary at 539 Ma, it implies the key evolutionary expansion started before that threshold. The assemblage links late Ediacaran communities with early Cambrian biotas, pushing the start of the so-called Cambrian explosion into the late Ediacaran.

The team led by Luke Parry and Frankie Dunn, with UK and Chinese collaborators, identified both previously described and newly recognized taxa, including what they interpret as the oldest known deuterostomes. Some of these specimens are acorn worms, organisms that can live in U-shaped burrows and feed with paired tentacles. The fossil evidence supports earlier biological-sampling and trace-based hypotheses that deuterostomes predates the Cambrian, implying chordates were present in that same interval.

The study highlights bilateral symmetry as a major evolutionary innovation. Unlike radially symmetric taxa such as jellyfish, bilateral organisms better support directional movement and sensory centralization, including primary sensory organs in the head, a one-way gut with mouth and anus, and increasingly complex musculature and nervous systems. Imran Rahman notes that the assemblage closes the gap between the earliest fossil signal of deuterostomes and molecular estimates, supporting an Ediacaran-to-Cambrian transition rather than a sudden Cambrian onset. (Key numbers: 539)