LAUSR

The Paleocene-Eocene Thermal Maximum (PETM), the most well-studied transient 25 hyperthermal event in Earth history, is characterized by prominent and dynamic 26 changes in global marine ecosystems. Understanding such biotic responses provides 27 valuable insights into future scenarios in the face of anthropogenic warming. However, 28 evidence of the PETM biotic responses is largely biased towards deep-sea records, 29 whereas shallow-marine evidence remains scarce and elusive. Here we investigate a 30 shallow-marine microfaunal record from Maryland, eastern United States, to 31 comprehensively document the shallow-marine biotic response to the PETM. We 32 applied birth-death modeling to estimate the local diversity dynamics, combined with 33 evaluation of time-variable preservation artifacts. We discovered strong increase of 34 species disappearance and appearance predating the onset and at the final recovery 35 phase of the PETM, respectively. Our paleoecological analyses indicate that 36 bathymetric habitat compression due to extreme warmth and oxygen minimum zone 37 expansion caused shallow-marine benthic species extirpation and ecosystem 38 perturbation during the PETM; and that rapid recovery and diversification followed 39 the PETM disaster, thus contributing new understanding to the shallow-marine biotic 40 changes in a broad context of global warming. 41