789-million-year-old rocks lack animals despite ideal fossil preservation
Fossilisation processes and our reading of animal antiquity
Burgess Shale-type (BST) preservation, which captures soft-bodied animals in Cambrian mudstones, is rare in Neoproterozoic deposits. In the few assemblages with BST conditions dated to 789 million years ago or older, no animals have been identified, suggesting they had not evolved by then. This provides a soft maximum age constraint on crown group animals of 789 million years ago, reconciling molecular clock estimates with the fossil record.
Burgess Shale-type conditions are rarely associated with Neoproterozoic fossil biotas, but in the few assemblages with these conditions, dated to 789 million years ago or older, no animals have been identified, suggesting they had not evolved by this time.