Retreat, Resilience, and Reorganization: Decoding the Post-Paleozoic Evolution of Brachiopods

The Paleozoic–Modern Evolutionary Fauna transition is defined by the ecological replacement of brachiopods by bivalves. However, it remains debated whether post-Paleozoic brachiopods experienced a simple, continuous global decline or a complex macroevolutionary reorganization. Previous studies are often limited by ecological mismatches, uncorrected sampling biases, and single taxonomic scales. To resolve this, this study presents a high-resolution analysis of brachiopod evolution from the Triassic to the Quaternary. Using Paleobiology and Geobiodiversity Database records, I applied coverage-based standardization and, for guild-level comparisons, strict ecological filtering, comparing brachiopods only to ecologically equivalent bivalves and echinoderms. Results reveal three major patterns. First, regional and global diversity decoupled: global diversity showed Mesozoic diversification pulses, whereas the Chinese record exhibited a sustained post-Triassic collapse, showing global aggregates mask regional extirpations. Second, brachiopods displayed strong hierarchical resilience: environmental crises drastically pruned species richness (causing generic monotypy), yet family-level diversity remained remarkably stable. Third, brachiopods underwent a macroecological reorganization, retreating from carbonate reefs and shifting poleward to establish their modern anti-tropical distribution. Ultimately, the post-Paleozoic history of brachiopods is not a passive decline, but a multi-dimensional reorganization driven by regional habitat loss, geographic redistribution, and deep-lineage survival.