Data from Cretaceous-Paleogene plant extinction and recovery in Patagonia

The Cretaceous-Paleogene (K/Pg) extinction appears to have been
geographically heterogeneous for some organismal groups. Southern
Hemisphere K/Pg palynological records have shown lower extinction and
faster recovery than in the Northern Hemisphere, but no comparable,
well-constrained Southern Hemisphere macrofloras spanning this interval
had been available. Here, macrofloral turnover patterns are addressed for
the first time in the Southern Hemisphere, using over 3,500 dicot leaves
from the latest Cretaceous (Maastrichtian) and the earliest Paleocene
(Danian) of Argentine Patagonia. A maximum ca. 90% macrofloral extinction
and ca. 45% drop in rarefied species richness is estimated across the
K/Pg, consistent with substantial species-level extinction and previously
observed extirpation of host-specialized leaf-mines. However, prior
palynological and taxonomic studies indicate low turnover of higher taxa
and persistence of general floral composition in the same sections. High
species extinction, decreased species richness, and homogenous Danian
macrofloras across time and facies resemble patterns often observed in
North America, but there are several notable differences. When compared
with boundary-spanning macrofloras at similar absolute paleolatitudes (ca.
50⁰S or N) from the Williston Basin (WB) in the Dakotas, both
Maastrichtian and Danian Patagonian species richness are higher, extending
a history of elevated South American diversity into the Maastrichtian.
Despite high species turnover, our analyses also reveal continuity and
expansion of leaf morphospace, including an increase in lobed and toothed
species unlike the Danian WB. Thus, both Patagonian and WB K/Pg
macrofloras support a significant extinction event, but they may also
reflect geographically heterogeneous diversity, extinction, and recovery
patterns warranting future study.