Annelids from the Cambrian (Wuliuan Stage, Miaolingian) Spence Shale Lagerstätte of northern Utah, USA.

The Spence Shale Member of the Langston Formation in northern Utah and southern Idaho preserves generally non-biomineralized fossil assemblages referred to as the Spence Shale Lagerstätte. The biota of this Lagerstätte is dominated by panarthropods, both biomineralized and soft-bodied examples, but also preserves diverse infaunal organisms, including species of scalidophorans, echinoderms, lobopodians, stalked filter feeders, and various problematic taxa. To date, however, only a single annelid fossil, originally assigned to Canadia sp., has been described from the Spence Shale. This lone specimen and another recently collected specimen were analyzed in this study using scanning electron microscopy and energy dispersive X-ray spectrometry. The previous occurrence is reassigned to Burgessochaeta cf. B. setigera Walcott, 1911. The new fossil, however, is identified as a novel polychaete taxon, Shaihuludia shurikeni gen. et sp. nov., characterized by the presence of fused, bladed chaetae and a wide body. The occurrence of Burgessochaeta is the first outside the Burgess Shale and its vicinity, whereas Shaihuludia shurikeni gen. et sp. nov. adds to the diversity of annelids in the middle Cambrian and highlights the diversity of the Spence Shale Lagerstätte.

Decoupling biogeochemical records, extinction, and environmental change during the Cambrian SPICE event.

Several positive carbon isotope excursions in Lower Paleozoic rocks, including the prominent Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE), are thought to reflect intermittent perturbations in the hydrosphere-biosphere system. Models explaining these secular changes are abundant, but the synchronicity and regional variation of the isotope signals are not well understood. Examination of cores across a paleodepth gradient in the Upper Cambrian central Missouri intrashelf basin (United States) reveals a time-transgressive, facies-dependent nature of the SPICE. Although the SPICE event may be a global signal, the manner in which it is recorded in rocks should and does vary as a function of facies and carbonate platform geometry. We call for a paradigm shift to better constrain facies, stratigraphic, and biostratigraphic architecture and to apply these observations to the variability in magnitude, stratigraphic extent, and timing of the SPICE signal, as well as other biogeochemical perturbations, to elucidate the complex processes driving the ocean-carbonate system.