The latitudinal diversity gradient (LDG) is recognized as one of the most pervasive, global patterns of present-day biodiversity. However, the controlling mechanisms have proved difficult to identify because many potential drivers covary in space. The geological record presents a unique opportunity for understanding the mechanisms which drive the LDG by providing a direct window to deep time biogeographic dynamics. Here we used a comprehensive database containing 52,318 occurrences of marine fossils to show that the shape of LDG changed greatly during the Permian-Triassic mass extinction from showing a significant tropical peak to a flattened LDG. The flat LDG lasted for the entire Early Triassic (~5 million years) before reverting to a modern-like shape in the Middle Triassic. The environmental extremes that prevailed globally, especially the dramatic warming, likely induced selective extinction in low latitudes and accumulation of diversity in high latitudes through origination and poleward migration, which combined together account for the flat LDG of the Early Triassic.

Database S1. Late Permian-Triassic fossil database

This database consists of occurrences of marine genera from the late Permian (Changhsingian - 254.1 Ma) to the Late Triassic (Rhaetian - 201.3 Ma) and includes 52,318 generic occurrences at a substage- or stage-level resolution from 1768 literature sources.

Database S2. Late Permian-Middle Triassic conodont oxygen isotope

This database consists of 616 oxygen isotope measurements from the Late Permian Changhsingian to the Middle Triassic Anisian.

Supporting Information

This file contains a PDF file that includes supplementary data and figures that support the manuscript. It includes figures S1-S4 and tables S1-S6.