Staking out the frontiers: The limits of the metazoan shallow marine fossil record.

The fossil record is inherently incomplete, yet its physical limits remain largely uncharted. Here, we quantify the spatiotemporal coverage of the global shallow-marine metazoan fossil record across the Phanerozoic, using a large dataset of georeferenced collections intersected with global geological data. Modeling historical sampling trajectories, we show that for most time intervals, future data accumulation is expected to be negligible, and geographic coverage is approaching saturation. For intervals with remaining potential, we reconstruct the present-day extent of unexplored but geologically accessible strata, providing spatially explicit guidance on where undetected fossil information is most likely to await discovery. Our results constitute a quantitative roadmap for prioritizing fieldwork, completing occurrence databases, and mobilizing unpublished museum collections.