Paleogeography modulates marine extinction risk throughout the Phanerozoic

Understanding the factors that have influenced the intensity and
selectivity of extinction throughout Earth history is critical for
explaining past biodiversity loss and associated implications for the
present biotic crisis. Here, we investigate the role of coastline geometry
and paleogeographic boundary conditions in shaping extinction risk for
shallow-marine-restricted taxa across 540 million years of Earth history.
Our findings reveal that interactions between the geographic distributions
of taxa and the geometric configurations of continental margins
significantly predict relative extinction risk throughout the Phanerozoic:
taxa with longer potential dispersal pathways, often associated with
east-west oriented coastlines, islands, or inland seaways, consistently
exhibit higher extinction risk than taxa with shorter potential dispersal
pathways. In contrast to many other predictors of extinction risk,
dispersal distance selectivity is amplified during mass extinction events
and hyperthermal intervals, suggesting geographic constraints become more
important during periods of rapid climate change. Our results provide
another potential mechanism for the generally elevated extinction rates
during the Paleozoic, an interval characterized by complex inland seas and
a preponderance of east-west coastlines. These insights underscore the
importance of considering paleogeographic context when interpreting
extinction patterns and assessing implications for future biodiversity
loss.