Opportunistic behaviour of invertebrate marine tracemakers during the Early Triassic aftermath of the end-Permian mass extinction

A regional field study of ichnocoenoses in the Griesbachian Dinwoody Formation and the Smithian Sinbad Limestone Member revealed that benthic invertebrate tracemaking populations exhibited aspects of opportunistic behaviour following the end-Permian mass extinction. This study represents the first documentation of population strategies of ichnocoenoses following a mass extinction event. These trace fossil assemblages are characterised by low-to-moderate ichnodiversity, low-to-moderate bioturbation, small burrow widths, non-specialised behaviour and shallow tiering. Our data combined with other published studies indicate that various ecological characteristics of ichnocoenoses differed by environment, paleolatitude and stage through the Early Triassic. The pattern of opportunistic behaviour is likely attributed to repeated intervals of deleterious environmental conditions similar to those that caused the end-Permian mass extinction.