Saproxylic arthropod borings in Nothofagoxylon woods from the Miocene of Patagonia

Abstract

Permineralized woods of Nothofagoxylon scalariforme from Miocene strata (Río Leona Formation) that crop out in the southwestern region of Santa Cruz Province, Argentina were studied. Six types of borings are described, filled with coprolites or homogeneous excrement masses (frass). Based on size, shape, orientation and content, the borings can be related to oribatid mites (Acari: Oribatida), beetles (Insecta: Coleoptera) and springtails (Insecta: Collembola). The host woods show fungal decay and are colonized by hyphae and spores, which suggest various forms of interaction with the arthropods and the Nothofagoxylon trees. The possible types of interactions developed between different organisms involved in the excavation, consumption and degradation of fossil woods in Miocene forests of Patagonia are discussed. Collectively, this evidence indicates that the analyzed woods were in an advanced state of decay prior to their fossilization and that several groups of organisms were active participants in the decomposition of woody substrates, or used them as nesting places, in early Neogene forest ecosystems of Patagonia.