Biodiversity can be interpreted in many ways. Classifications can include biotic and/or abiotic components, depend on scale and context, and often reflect the disciplinary bias of the authors. Marine biodiversity has almost exclusively been examined at the scale of local or modern processes, which are often less informative than biogeographic or ancient processes for understanding species richness patterns. However, modern and ancient processes are the endpoints of a natural hierarchy where different processes influence distribution at each level. Patterns and processes of biodiversity are scale dependent, with lower levels fully or partially nested in those above. Comparisons that omit this scale dependency will be compromised. We present here a hierarchical framework for describing the structure of marine demersal biodiversity across all spatial scales. This system explicitly recognizes the overarching influence of large-scale biodiversity patterns at realm (ocean basin and tectonic), provincial (palaeohistorical) and bathomic (depth-related) levels. The functional roles and spatial scales are captured within ten nested levels within realms, where the first seven are primarily spatially nested and ecosystem based, and the lowest levels represent units of taxonomic inheritance. The framework is conceptual and each level needs to be validated for its general applicability.