SUBSEQUENT BENTHIC BIOTIC CRISES IN THE WAKE OF THE LATE PERMIAN MASS EXTINCTION EVENT
Quantitative relative-abundance data of fossil benthic macroinvertebrates were collected from rocks in northern Italy that were deposited in a mixed siliciclastic-carbonate ramp setting on the northwestern margin of the Paleotethys Ocean that provides a continuous fossil record through the entire Early Triassic. Taxonomic diversity of the Werfen Formation shows elevated extinction rates during the Dienerian and at the Smithian/Spathian boundary. Functional richness - a measure of ecological diversity - was, however, only demonstrably affected in the late Dienerian in association with a cluster of isotope perturbations. Benthic assemblages from the Griesbachian, Dienerian and Smithian have very similar compositions, mainly characterised by various cosmopolitan bivalve, gastropod and microconchid biofacies. A significant change in composition was recorded across the Smithian/Spathian boundary with a change to Natiria costata, Neoschizodus ovatus and Holocrinus biofacies. Our results show, therefore, that the recovery of benthic ecosystems was interrupted by additional crises in the late Induan (Dienerian) and mid-Olenekian (Smithian/Spathian) only.