Subsequent crises delayed post-Permian benthic recovery

1 late Permian mass extinction event in northern Italy. ABSTRACT 10 The late Permian mass extinction event was the largest biotic crisis of the Phanerozoic and has 11 the longest recovery interval of any extinction event. It has been hypothesised that subsequent 12 carbon isotope perturbations during the Early Triassic are associated with biotic crises that 13 impeded benthic recovery. We test this hypothesis by undertaking the first high-resolution study 14 of the rock and fossil records of the entire Werfen Formation, Italy. Here, we show that elevated 15 extinction rates were recorded not only in the Dienerian, as previously recognised, but also 16 around the Smithian/Spathian boundary. Functional richness increases across the 17 Smithian/Spathian boundary associated with elevated origination rates in the lower Spathian. 18 The taxonomic and functional composition of benthic faunas also only recorded two significant 19 changes during the deposition of the Werfen Formation: with reduced heterogeneity in the 20 Dienerian and a turnover across the Smithian/Spathian boundary. The elevated extinctions and 21 compositional shifts in the Dienerian and across the Smithian/Spathian boundary are associated 22 with a negative and positive isotope excursion, respectively, which supports the hypothesis that 23 subsequent biotic crises are associated with carbon isotope shifts. The Spathian fauna represents 24 a more advanced ecological state not recognised in the previous members of the Werfen 25 Formation with increased habitat differentiation, shift in the dominant modes of life, appearance 26 of stenohaline taxa and the occupation of the erect and infaunal tiers. In addition to subsequent 27 biotic crises delaying the recovery, therefore, persistent environmental stress limited the 28 ecological complexity of benthic recovery prior to the Spathian.