Synchrotron X-ray imaging reveals the three-dimensional architecture of beetle borings (Dekosichnus meniscatus) in Middle–Late Jurassic araucarian conifer wood from Argentina

Abstract

Longitudinally aligned borings attributed to the ichnotaxon Dekosichnus meniscatus in the inner secondary wood of a silicified Middle–Late Jurassic conifer from Argentina contain finely granular frass particles arranged in meniscoid laminae. Synchrotron X-ray computed tomographic reconstruction of the borings reveals new characters of this ichnotaxon, such as opposing orientations of menisci in some adjacent borings, regular spacing of minor and major meniscoid laminae, a scarcity of tunnel branching, and rare occurrences of cylindrical–spherical terminal chambers on excavations. Architectural and distributional features of the galleries suggest excavation by cerambycid beetle larvae, thus representing one of the earliest potential fossil records of this group. The borings are confined to the inner wood of a young tree that experienced a moderately seasonal climate in a volcanically influenced landscape. By detecting subtle heterogeneities in composition, this study demonstrates that high-energy synchrotron X-ray tomography can characterize anatomical features and complex ecological interactions within even densely permineralized (silicified) plant fossils.