Organisms that colonize wood are subject to a taphonomic tragedy—the richer and more diverse they become, the greater the deterioration of the host wood and the less likely such communities are to be fossilized. Moreover, palaeobotanical studies of fossil wood usually focus on the plant tissue, neglecting the evidence of parasitic, saproxylic, and other contained organisms. Such a case involved a relatively well-known fossil wood assemblage from the Santonian (Late Cretaceous, ca 84 Ma) of southeast Africa. In a set of 150 thin sections of silicified wood stored in the Senckenburg Museum for more than half a century, we discovered evidence of a diverse biotic community comprising bacteria, fungi, nematodes, several types of arthropods, and marine bivalves. These body fossils and traces, together with growth-ring features, fossil log size and shape, and the distribution of glauconite, facilitated interpretation of the multi-stage evolution of a wood-hosted biocoenosis of unprecedented diversity. This record is unique for the Mesozoic and is of importance for understanding the taphonomic pathways to preservation and the evolution and diversification of saproxylic and other wood-hosted communities in terrestrial and marine settings.