Ecologic stability of the dysaerobic biofacies during the Late Paleozoic

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Abstract
Late Plaeozoic faunas found in sediments of dysaerobic origin represent a unique community type that remained essentially unchanged from the Middle Devonian to the Early Permian. This dysaerobic community had the following unique characteristics: (1) dominance by vagile molluscs, with suspension-feeding brachiopods, bryozoans, corals and echinoderms usually subordinate; (2) a trophic structure dominated by deposit feeders and carnivorous or scavenging cephalopods; (3) small body size as the result of high juvenile mortality and possibly stunting; and (4) preservation of most individuals as pyritic steinkerns. All these characteristics are directly linked to the low oxygen levels of the dysaerobic environment. The relative stability of the deeper water, dysaerobic environment is consistent with Sanders'' Stability-Time Hypothesis. The dysaerobic environment apparently offered a refuge for more archaic biotas that evolved in nearshore environments of the early Paleozoic.