Abstract

Ediacaran and Cambrian fossils provide direct evidence of early animal evolution, which is lucky because we couldn’t have predicted what we see. Researchers flock to the spectacular macrofossil assemblages at Mistaken Point, the Burgess Shale and Chengjiang (and with good reason!). But a powerful complementary dataset is emerging from “small carbonaceous fossils” (SCFs), which can be extracted from mudstones using careful acid-maceration, revealing exquisite preservation of animal cuticles, in particular. Rarely, the whole animal is preserved, as in recently discovered meiofaunal loriciferans from the upper Cambrian, just a third of a millimetre long. More commonly, the animals are in bits – but even fragmentary jaws, scalids and setae can re-write the history of arthropods, priapulids and annelids. SCFs help us to fill in the blanks between macrofossil Lagerstätten, but so far we have not uncovered a cryptic record of pre-Cambrian animals. Instead, we see more evidence for animal disruption of a microbial biosphere around the Ediacaran–Cambrian transition.