Biotic recovery from the end-permian mass extinction: Behavior of the inarticulate brachiopod Lingula as a disaster taxon

Disaster taxa are long-ranging opportunistic generalists that briefly proli ferate in the aftermath of mass extinctions, invading vacant ecospace until forced to return to more marginal settings through competition with specia list taxa returning from refugia. Lowermost Triassic (Griesbachian) strata worldwide have been noted for a brief 'proliferation of lingula: a classic 'living fossil', which through its long fossil record typically has occurre d in shoreface and dysoxic settings. The abundance of Lingula relative to o f her taxa in the Griesbachian Dinwoody Formation of southwestern Montana a nd western Wyoming(USA) has been quantified and the results placed into a p aleoenvironmental context. Lingula dominates the fossil assemblage in the D inwoody Formation across several facies deposited on an oxygenated storm-do minated, mixed carbonate/siliciclastic shelf: A study of preservational sta te and quality further indicates that these results are not due to taphonom ic bias. Lingula, therefore, behaved as a disaster taxon during the biotic recovery from the end-Permian. mass extinction, much like relatively common Early Triassic normal marine stromatolites, that have been interpreted as disaster forms. Thus, while the fundamental rules of geology and biology ha ve not changed, during biotic recoveries from mass extinctions organisms ma y behave and interact with their environments very differently than do thei r modern or fossil equivalents in "normal" times.