ARTHROSQUAD ASSEMBLE! RECENT AND FORTHCOMING DESCRIPTIONS OF ARTHROPODS UNIQUE TO THE WAUKESHA LAGERSTÄTTE

The Silurian Waukesha biota from the peritidal Brandon Bridge Formation near Waukesha, Wisconsin was first described by Don Mikulic, Joanne Kluessendorf, and Derek Briggs in 1985, and then in greater detail by Kluessendorf in 1990. While some taxa have since been named and described, several of the unique non-trilobite arthropods have yet to be formally classified. Herein, we provide an overview of three recent and/or forthcoming descriptions of non-trilobite arthropods of the Waukesha Lagerstätte, along with a summary of their taphonomy.

Although outwardly similar to Burgess Shale-type preservation, SEM-EDS analysis reveals that these taxa are primarily preserved via phosphatization, with lesser kerogenization and minor pyritization. The extent of phosphatization appears to be taxon-specific, and originally biomineralized taxa are now demineralized or remineralized with francolite. Demineralized conulariids may have provided the phosphate necessary to drive the secondary phosphatization of the soft-bodied taxa. The Waukesha Lagerstätte occupies a unique window of geologic time, and thus the soft-bodied fauna preserved therein have the potential to provide insight into the evolutionary history of arthropods between those well-known from earlier and later Paleozoic deposits.

The following three taxa belong to novel arthropod genera from the Waukesha Lagerstätte: 1) the common Acheronauta stimulapis gen. et sp. nov. (proposed) and rare Acheronauta leonidae gen. et sp. nov. (proposed) representing two morphologies of a crustacean-like arthropod bearing a head carapace, a suite of raptorial appendages, and a long, segmented trunk adorned with small swimming appendages; 2) the uncommon Parioscorpio venator Wendruff et al., 2020, originally described as a scorpion and recently reevaluated by Anderson et al. 2021 as basal to both crown-group Mandibulata and Chelicerata; and 3) the uncommon Papiliomaris kluessendorfae gen. et sp. nov. (proposed), previously considered to be a marellomorph now reinterpreted as a crustacean-like, bivalved, filter-feeding arthropod. This last taxon is intended to be named in honor of Joanne Kluessendorf, due to her instrumental role in both the discovery and original description of the Waukesha Lagerstätte.