An exceptional window into Carboniferous arthropod diversity and taphonomy from the Westphalian of central Germany

Arthropods are one of the most successful groups in continental ecosystems. Unfortunately, their fossil record is incomplete, due to the low preservation potential of their fragile exoskeletons and collection bias related to their mostly small size. This study elucidates the arthropod diversity and their fossilization pathways in the Pennsylvanian Zwickau Formation (Westphalian D, Zwickau-Oelsnitz Basin, central Germany). For 150 years, these strata have been known to yield well-preserved arachnids, myriapods and pterygote insects, including large-winged blattoids and Kreischeria wiedei, the largest known trigonotarbid. Detailed study of the embedding architectures and the fossils—involving HF maceration as well as combined transmitted-light and epifluorescence microscopic analysis—reveal an unusually diverse community that inhabited an intramontane peat-forming wetland near alluvial fans. The arthropod remains mainly occur in dm-thick distal crevasse-splay deposits. Accumulation and preservation of the arthropods was likely facilitated via rapid, (sub)autochthonous burial in water-logged overbank sediments that faced limited rhizoturbation after deposition and formed repeatedly due to the tropical, humid climate. As a result, the Zwickau strata became an extraordinary archive for delicate arthropod body fossils. Outstanding examples comprise a unique group of five phalangiotarbids. Various trigonotarbids are available in different preservation types and even reveal insights into their detailed three-dimensional cuticle morphology. HF maceration provided a considerable content of arthropod cuticle remains in the deposits, once more highlighting the significance of host rock processing and mesofossil analysis for filling the gaps in the arthropod fossil record.