Abstract

Reefs are widely supposed to be particularly susceptible to mass-extinction events, and to survive only as low-diversity, remnant communities dominated by holdover or disaster taxa. Famennian (Late Devonian) reefs exposed in the Windjana Limestone of the Canning basin, northwestern Australia, demonstrate, however, that a novel reef ecology was established in the immediate aftermath of the Frasnian-Famennian mass extinction. Here, diverse calcimicrobes (including Rothpletzella spp., Shuguria spp., Ortonella, and Girvanella), together with bryozoans, brachiopods, and stromatoporoid, sphinctozoan, and lithistid sponges, grew as complex framework intergrowths in previously undocumented morphological forms, forming spectacular elevated laminar to platy structures to 3 m in diameter and 0.35 m thick. At least 15 morphospecies of lithistids are now identified, where only two were previously documented. These communities show no substantial reduction in biodiversity compared to Frasnian counterparts, nor any change in tiering or loss of complex ecological interactions. These observations suggest that where stable carbonate platforms persisted after mass-extinction events, reef building could continue. More important, they demonstrate that no protracted interval of time was necessarily required either for recovery to ecological stability or for completely new reef ecologies to assemble. Such studies highlight the need to document ecosystem recovery after mass-extinction events using detailed paleoecological analyses in addition to simple compilations of global biodiversity changes.

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