In This Issue

Angiosperms diversified quickly during the Cretaceous period, reshaping a world previously dominated by ferns and conifers. Anne-Claire Chaboureau et al. (pp. 14066–14070) simulated global climate changes during the break-up of the Pangea supercontinent to assess the possible influence of the changes on angiosperm expansion. Using ocean–atmosphere general circulation models, the authors observed increases in rainfall over continental land masses during the beginning of the Pangea break-up from the Triassic period to the late Cretaceous, bringing rain to areas that were previously arid deserts. Temperate biome area increased from 25% of simulated landmass 225 million years ago to more than 45% of simulated landmass by 95 million years ago. Further, the authors examined the locations of angiosperm fossil sites during the Cretaceous and noted that fossil sites became more diverse and geographically scattered over time and expanded into northern latitudes during the mid-Cretaceous period. According to the authors, the fraction of angiosperm fossil sites located in temperate biomes doubled between the Aptian and Cenomanian ages. The results suggest that abiotic factors, such as Cretaceous climate change, rising sea level, and the formation of isolated archipelagos, may have contributed to the sudden rise of angiosperm diversity, according to the authors. — P.G.