Small carbonaceous fossils (SCFs): A new measure of early Paleozoic paleobiology

Use of a low-manipulation hydrofluoric acid-extraction procedure on Cambrian mudstones reveals an unexpectedly abundant and diverse range of small carbonaceous fossils (SCFs), primarily the disarticulated sclerites and cuticular fragments of animals. Relatively recalcitrant forms such as Wiwaxia sclerites and priapulid-like scalids are sufficiently common to yield a reasonably reliable biostratigraphic signal, unlike their rare macroscopic counterparts. Molluscan radulae, crustacean appendages, and the carbonaceous components of originally mineralized metazoan sclerites provide further insights into the histology, diversity, and distribution of early metazoans. The widespread occurrence of SCFs is due in part to their enhanced biostratinomic potential for transport, burial, and preservation, particularly in well-aerated epicratonic settings not represented by Burgess Shale-type macrofossils. More generally, the SCF record represents a largely untapped measure of ecological and evolutionary dynamics through the early Paleozoic.