Abstract:
The Clouston Farm locality, assigned to the Lopingian Epoch and occurring within the Normandien Formation of the northeastern Karoo Basin, provides evidence for a community of diverse vascular plants occupying riparian woodland. The depositional environment is interpreted as an abandoned trunk channel that preserved a megaflora in slack-water phases punctuated by overbank deposits from rare flood events. Of 9772 plant specimens tabulated from an unbiased census of all fragments greater than ~ 1 cm2, there are 51 distinct organ morphotypes, including glossopterids, sphenopsids, and ferns, collectively represented as foliage, axes, fructifications, and dispersed seeds. Of the 11 most abundant morphotypes 10 are glossopterid morphotypes or variant subtypes, in addition to a sphenopsid. Glossopterid morphotype dominance also is reflected in the palynoflora. Palynological data indicate a Wuchiapingian age for the locality. A specimen of the dicynodont [`]Oudenodon,' found in a nearby stratigraphically equivalent outcrop, is attributable to the Dicynodon Assemblage Zone, assigned a younger Changhsingian age. A rich record of plant-insect associations demonstrates an elevated frequency of external foliage feeding by mandibulate insects and lower incidence of oviposition by palaeodictyopteroid and odonatopteroid taxa. Evidence for piercing-and-sucking and galling is rare. The most abundant plant taxon (glossopterid Morphotype C2a) is the most intensively herbivorized, overwhelmingly by external feeding and ovipositing insects. Insect damage on this host is beyond that predicted by floristic abundance alone. This specificity, and high herbivory levels on other glossopterid taxa, demonstrates extension of the Euramerican pattern toward the preferential targeting of pteridosperms. The Clouston Farm site provides a glimpse into a late Permian ecosystem of primary producers, herbivores, and insectivores--a prelude to the crisis that engulfed life at the end of the period.
