The Tommotian phase of the Early Cambrian Agronomic Revolution in the carbonate mud environment of central Siberia

The profound ecological change of the marine benthos that eventually led to thealmost complete destruction of the Precambrian matgrounds by benthic grazers andbioturbators (the agronomic revolution) was largely completed in the Tommotian. Atthat time, burrows produced by bottom-dwelling animals as shelters against predatorswere supplemented by burrowing for food by predators and sediment feeders. Thelimy mud ichnofauna of that age in Siberia was very different from the roughly coevalsand bottom faunas of Baltica. Although the exact zoological identity of the animalsforming the infaunal Tommotian traces remains unknown, they probably mostly rep-resent various kinds of early nemathelminthes. No apparent locomotion traces of mol-lusc origin have been encountered in the Early Cambrian, despite the abundantoccurrence of skeletal fossils attributed to molluscs. Possibly the standard muscularfoot, typical of modern molluscs, had not yet developed. Ichnotaxa represented areTeichichnusisp.,Rhizocoralliumisp.,Chondritesisp., possibly the Buren ichnocomplexand  others.