Understanding the uneven distribution of species across space is a key goal of evolutionary biology and macroecology. Today’s biodiversity hotspots are a snapshot of current conditions, and understanding their origin requires a perspective that reaches back in time. In the modern marine realm, the Indo-West Pacific is a biodiversity hotspot for many groups, including corals, bivalves, and fishes. Modern marine fish diversity in the IWP is well known, but there is a substantial gap in our understanding of its ancient history. My research focuses on understanding the uneven distribution of marine fish taxa in the Cenozoic by reviewing and comparing fossil marine tropical fishes throughout the Paleogene and Neogene of the larger Indo-West Pacific and testing the collapse of the previous marine biodiversity hotspot (Tethys).