EXTINCTION AND RECOVERY OF GONDWANAN PLANT AND HERBIVOROUS ARTHROPOD COMMUNITIES THROUGH THE PERMIAN-TRIASSIC BIOTIC CRISIS IN SOUTHERN HIGH PALAEOLATITUDES

The Sydney Basin, Australia, incorporates a relatively continuous continental Upper Permian to Middle Triassic sedimentary succession. A current multi-disciplinary study of outcrop sections and bore cores is providing precise constraints on the age, depositional settings, geochemical characteristics, palaeoclimate and fossil content of this succession. These strata represent one of the very few successions in the world hosting relatively rich Early Triassic plant macrofossil assemblages that, in conjunction with palynological data, enable analysis of the recovery of plant communities in the aftermath of the end-Permian extinction event (EPE). Sydney Basin Late Permian plant fossil assemblages are overwhelmingly dominated by deciduous broad-leafed glossopterid gymnosperms typifying extensive high-palaeolatitude micro- to mesothermal wetland communities. An abrupt collapse in glossopterid-dominated ecosystems and cessation of peat accumulation characterizes the EPE in the Sydney Basin. A succeeding plant community represented by assemblages from a generally <3 m package of dark shales immediately overlying the uppermost coal seam is characterized by an influx of peltaspermalean seed-ferns and voltzialean conifers with generally small sclerophyllous leaves. Pleuromeian lycophytes are also present together with very rare hold-over elements of the preceding glossopterid communities. Progressive diversification of plant assemblages is evident through the Lower Triassic succession, with umkomasiacean (corystosperm) taxa attaining dominance during the Olenekian. A general increase in leaf size among the dominant plants together with the re-appearance of coaly laminae suggests a return to more humid conditions around the end of the Early Triassic. A similar pattern of vegetation turnover is apparent in the less intensely sampled Permian-Triassic succession in the Prince Charles Mountains, East Antarctica. Arthropod damage is common and diverse on Late Permian glossopterid plants across Gondwana. Damage features on immediate post-EPE plant remains are sparse and dominated by simple margin-feeding injuries. By the late Olenekian, foliar damage types are notably more abundant and complex attesting to synchronous recovery of plant and terrestrial arthropod communities.