Animal diversity blossomed around 541 million to 509 million years ago, when most of today’s major animal groups arose. Now, palaeontologists have discovered another window into that spectacular event, known as the Cambrian explosion.

At about 518 million years of age, the fossil bed discovered in South China is slightly older than the celebrated Burgess Shale, a fossil site in the Canadian Rocky Mountains where the forms of hundreds of Cambrian animals have been immaculately preserved. Calling their assemblage the Qingjiang biota, Xingliang Zhang, at Northwest University in Xi’an, China, and his colleagues identify several algal forms and 101 types of animal — over half of which were never before described.

The collection’s abundance of early pristine fossils of squishy animals, such as jellyfish, sea anemones and comb jellies, could be useful for biologists exploring early animal origins. The beds also hold unusually large species of mud dragon, or kinorhynchs; modern-day versions of these moulting invertebrates are visible only under a microscope.

The biota includes animals known from just a handful of fossils in other Cambrian-era beds. Those will teach biologists more about dozens of creatures that have long since gone extinct.