Palaeoecology of the Early Cambrian Sinsk biota from the Siberian Platform

The Sinsk biota (Early Cambrian, Botoman Stage, Siberian Platform) inhabited an open-marine basin within the photic zone, but in oxygen-depleted bottom waters. Its rapid burial in a fine-grained sediment under anoxic conditions led to the formation of one of the earliest Cambrian Lagerstنtte. All the organisms of the biota were adapted to a life under dysaerobic conditions. It seems possible that the adaptations of many Cambrian organisms, which composed the trophic nucleus of the Sinsk Algal Lens palaeocommunity to low oxygen tensions allowed them to diversify in the earliest Palaeozoic, especially during the Cambrian. Nowadays these groups comprise only a negligible part of communities and usually survive in settings with low levels of competition. Nonetheless, the organization of the Algal Lens palaeocommunity was not simple, it consisted of diverse trophic guilds. The tiering among sessile filter-feeders was well developed with the upper tier at the 50 cm level. In terms of individuals, the community was dominated by sessile filter-feeders, vagrant detritophages, and diverse carnivores/scavengers. The same groups, but in slightly different order, comprised the bulk of the biovolume: vagrant epifaunal and nektobenthic carnivores/scavengers, sessile filter-feeders, and vagrant detritophages. The Algal Lens and Phyllopod Bed (Burgess Shale) Lagerstنtten share a number of common features including a representativeness of certain groups, a relative percentage of fauna in terms of individuals and biovolumes, feeding habits, and substrate relationships.