Widespread preservation of small carbonaceous fossils (SCFs) in the early Cambrian of North Greenland

The early Cambrian (ca. 518 Ma) Sirius Passet Lagerstätte of North Greenland is one of the most celebrated sites bearing fossils of soft-bodied organisms, and provides key insights into the Cambrian explosion of animal life. Unlike the younger Burgess Shale (508 Ma), the Sirius Passet biota does not preserve original carbonaceous material because of its history of metamorphic heating. Nearby sediments from within the same formation, however, have escaped the worst effects of thermal alteration. We report an entirely new diversity of metazoan remains preserved in a Burgess Shale–type fashion from sediments throughout the Buen Formation, in the form of small carbonaceous fossils (SCFs). The assemblages include the oldest known pterobranch hemichordates, diverse cuticular spines of scalidophoran worms, demineralized trilobite cuticle, bivalved arthropods (Spinospitella-like and Isoxys-like forms), protoconodonts, and a variety of less phylogenetically constrained metazoan and protistan forms. Together these SCFs capture exceptional microanatomical details of early Cambrian metazoans and offer new insights into taphonomic pathways at Sirius Passet and the nature of Burgess Shale–type preservation.