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Two extinction pulses in Permian–Triassic crisis

From: Ben Creisler

A new non-dino paper that may be of interest:

Haijun Song, Paul B. Wignall, Jinnan Tong & Hongfu Yin (2012)
Two pulses of extinction during the Permian–Triassic crisis.
Nature Geoscience (advance online publication)

The Permian–Triassic mass extinction is the most severe biotic crisis
identified in Earth history. Over 90% of marine species were
eliminated, causing the destruction of the marine ecosystem
structure3. This biotic crisis is generally interpreted as a single
extinction event around 252.3 million years ago, and has been
variously attributed to the eruption of the Siberian Traps or possibly
a bolide impact. Here we demonstrate that the marine extinction
consisted of two pulses, separated by a 180,000-year recovery phase.
We evaluated the range of 537 species representing 17 marine groups in
seven Chinese sections from a 450,000-year interval spanning the
Permian–Triassic boundary. The first stage of extinction occurred
during the latest Permian, and was marked by the extinction of 57% of
species, namely all plankton and some benthic groups, including algae,
rugose corals, and fusulinids. The second phase occurred in the
earliest Triassic, and resulted in the extinction of 71% of the
remaining species. This second extinction phase fundamentally altered
the marine ecosystem structure that had existed for the previous 200
million years. Because the two pulses showed different extinction
selectivity, we conclude that they may have had different
environmental causes.