Census of the Indian Springs Lagerstنtte, Poleta Formation (Cambrian), western Nevada, USA

Intervals of exceptional fossil preservation collectively termed the Indian Springs Lagerstنtte occur in the middle member of the Poleta Formation (Cambrian, Series 2, Stage 3) in Esmeralda County, Nevada, USA. The preserved macrofauna and taphonomic modes are similar to those of the Spence Shale Lagerstنtte of Utah (Cambrian Series 3). The Indian Springs macrofauna mostly consists of biomineralizing organisms such as trilobites, helicoplacoids, hyolithids and inarticulate brachiopods. Multi-element taxa such as helicoplacoids and chancelloriids are commonly articulated. Examples of preserved nonbiomineralized anatomy include mantle setae of brachiopods, demosponge skeletons, hyolithid gut tracts, trilobite appendages, algae, cyanobacteria, and body parts of nonbiomineralizing arthropods. The Indian Springs Lagerstنtte is dominated by fine siliciclastics, and was deposited in an offshore shelf setting subjected to storm-initiated sediment pulses. Exceptional preservation was facilitated by obrution-type deposition, presumably in dysoxic or anoxic muds, and in environments where organismic remains were removed from durophagous carnivores and scavengers, including bioturbators.