ECOSPACE OCCUPATION IN AN UNUSUALLY DIVERSE EARLY TRIASSIC MARINE ECOSYSTEM

It is maintained that the Permo-Triassic mass extinction (PTME), the most devastating loss of life in recorded Earth history, facilitated the transition from the Paleozoic Evolutionary Fauna (PEF) to that of the Modern Evolutionary Fauna (MEF). This shift suggests that Triassic paleocommunities were ecologically and physiologically different from those of the Permian. However, prior studies have largely focused on taxonomic diversity and global patterns in the PTME aftermath, with less attention being paid to the functional differences between survivors of the PEF and newly evolved members of the MEF during recovery. Here, we quantify the functional diversity and trait space of the recently discovered Early Triassic (Spathian) Paris Biota from southeastern Idaho. As the complex and highly diverse Paris Biota has been suggested to represent the rise of the MEF, the hypothesis tested here is that the Spathian Paris Biota represents a transitional paleocommunity containing a mixture of PEF (e.g., generally sessile, epifaunal) and MEF (e.g., active, infaunal) faunal traits in the aftermath of the PTME. Current data suggest that although there was significant functional continuity between the PEF and MEF at the PTME boundary, functional emphasis shifted, potentially resulting in the start of an ecological, macroevolutionary transformation. Furthermore, this fauna may represent a more complex ecosystem than has been previously documented in the early Triassic, in addition to being seemingly dominated by more active Mesozoic-style traits (i.e., high mobility, infaunality, non-suspension feeding, etc.) in the aftermath of the PTME. This has important implications for understanding the spatial and temporal pattern of ecospace occupation between marine paleocommunities in the aftermath of the PTME, as well as the complex relationship between taxonomic and functional diversity.