eLife Assessment
This manuscript describes valuable new material of small, unusually preserved fossils from deep in the Cambrian of China and argues they represent very early bilaterian animals such as annelids or panarthropods. The authors present convincing evidence of the fossilisation of specimens as microbial pseudomorphs, however, the fossils show few details and it is difficult to assess their affinity. The broader claims made about the timing and nature of the Cambrian explosion are inadequately supported by the material, given that bilaterians were already known to exist during that period.