Scientists have uncovered the earliest fossil evidence of annelids (ringed worms) in Cambrian microfossils dating back approximately 535 million years ago. This discovery offers fresh insights into the origin and early evolution of the annelids, a group of animals that includes bristle worms, earthworms, leeches, and peanut worms.

An international research team led by Chinese scientists has discovered the oldest known body fossils of annelids, extending the evolutionary record of a major animal group by more than 10 million years to 535 million years ago, according to the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS).

Around 539 million years ago, Earth witnessed the Cambrian explosion — a pivotal event when nearly all major animal groups suddenly emerged in the fossil record, reshaping the planet's biodiversity. However, this biological boom was interrupted by the Sinsk event around 513 million years ago. While scientists know this first mass extinction of the Phanerozoic — the starting age of visible life — caused widespread species loss, its full impact remained unclear due to a lack of soft-bodied fossils from the period immediately after the event.