The discovery of a rare fly in a North London cemetery marks my entry point into a wider reflection on the value and significance of urban biodiversity. Using different indices of ecological endangerment, along with a critical reading of new materialist insights, this paper explores the cultural, political, and scientific significance of saproxylic (rotten wood) invertebrate communities in an urban context. The paper brings the fields of urban ecology and post-humanism into closer dialogue to illuminate aspects to urban nature that have not been systematically explored within existing analytical frameworks. We consider a series of intersecting worlds, both human and non-human, as part of a glimpse into saproxylic dimensions to urban nature under a putative transition to a new geo-environmental epoch.