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End-Cretaceous plant extinction in Patagonia
From: Ben Creisler
A new non-dino paper in PLoS ONE that may be of interest:
Viviana D. Barreda, Nestor R. Cúneo, Peter Wilf, Ellen D. Currano,
Roberto A. Scasso & Henk Brinkhuis (2012)
Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity,
Low Extinction, and a Classopollis Spike.
PLoS ONE 7(12): e52455.
Nearly all data regarding land-plant turnover across the
Cretaceous/Paleogene boundary come from western North America,
relatively close to the Chicxulub, Mexico impact site. Here, we
present a palynological analysis of a section in Patagonia that shows
a marked fall in diversity and abundance of nearly all plant groups
across the K/Pg interval. Minimum diversity occurs during the earliest
Danian, but only a few palynomorphs show true extinctions. The low
extinction rate is similar to previous observations from New Zealand.
The differing responses between the Southern and Northern hemispheres
could be related to the attenuation of damage with increased distance
from the impact site, to hemispheric differences in extinction
severity, or to both effects. Legacy effects of the terminal
Cretaceous event also provide a plausible, partial explanation for the
fact that Paleocene and Eocene macrofloras from Patagonia are among
the most diverse known globally. Also of great interest, earliest
Danian assemblages are dominated by the gymnosperm palynomorphs
Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae.
The expansion of Classopollis after the boundary in Patagonia is
another example of typically Mesozoic plant lineages surviving into
the Cenozoic in southern Gondwanan areas, and this greatly supports
previous hypotheses of high latitude southern regions as biodiversity
refugia during the end-Cretaceous global crisis.