Ecological continuity and transformation after the Permo-Triassic mass extinction in northeastern Panthalassa

The Permo-Triassic mass extinction (PTME) is often implicated in the transition from the Paleozoic Evolutionary Fauna (PEF) to the Modern Evolutionary Fauna (MEF). However the exact timing and details of this progression are unknown, especially regarding the vacating and filling of functional ecological space after the PTME. Here we quantify the functional diversity of middle Permian and Early Triassic marine paleocommunities in the western US to determine functional re-organization in the aftermath of the PTME. Results indicate that while the PTME was selective in nature, many new Triassic taxa either re-filled functional roles of extinct Permian taxa or performed the same functional roles as Permian survivors. Despite this functional overlap, Permian survivors and new Triassic taxa differed significantly in their relative abundances within those overlapping functions. This shift in numerical emphasis, driven by an increase in abundance towards more MEF-style traits, may represent a fi...