Paleobiology and taphonomy of exceptionally preserved organisms from the Waukesha Biota (Silurian), Wisconsin, USA

The Silurian (Llandovery, Telychian) Waukesha Lagerstätte in the Brandon Bridge Formation of Wisconsin, USA, is preserved in a dolomitic plattenkalk representing deposition in a shallow-water sediment trap on a carbonate platform. Renewed study of the deposit demonstrates biodiversity far richer than previously reported and includes both biomineralizing and non-biomineralizing organisms. At present, remains of at least 12 animal phyla are known, in addition to algae and microorganisms. Of these, remains of cnidarians, brachiopods, mollusks and echinoderms were previously unknown from this deposit. The macrobiota is dominated by trilobites, graptolites, conulariids, non-biomineralizing arthropods (some of which were previously unreported), and some worms (palaeoscolecids and annelids). New abundant evidence of microbial mats and associated microbial structures indicates a thriving microorganismal community. Evidence, including remnants of preserved microbes on macrofossils, demonstrates that microbial processes played a leading role in both burial and preservation of non-biomineralizing tissues. This process, referred to as microbial entombment, is a biologically mediated sedimentary process by which organic remains are entombed within a microbial mat. •Detailed revision of the Waukesha Biota yielded many new members and phyla (+12).•Soft-tissues preserved on many arthropods including gut tracts of 3 trilobite species.•Body fossils of microbes noted for first time at the deposit (coccoid bacteria).•Microbially influenced sedimentary structures noted for first time at this deposit.•Depositional model (microbial entombment) proposed to explain exceptional preservation.