The Permian and Triassic represent a time of major global climate change from icehouse to hothouse conditions and significant (∼25°) northward motion of landmasses amalgamated in essentially one supercontinent, Pangea. The greatest of all mass extinctions occurred around the Permian-Triassic boundary (251 Ma), although there is no consensus regarding the cause(s). Recent studies have suggested a meteor impact and worldwide die-off of vegetation, on the basis of sparse local observations. However, new analyses of global Permian and Triassic plant data in a paleogeographic context show that the scale and timing of effects varied markedly between regions. The patterns are best explained by differences in geography, climate, and fossil preservation, not by catastrophic events. Caution should be exercised when extrapolating local observations to global-scale interpretations. At the other extreme, global compilations of biotic change through time can be misleading if the effects of geography, climate, and preservation bias are not considered.

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