Mesozoic paleogeography and early angiosperm history

During the Early Cretaceous, ocean-floor spreading gradually opened up the tropical Atlantic and the Indian Ocean basin widened as the eastern segments of Gondwanaland were conveyed farther apart. At the same time, epeiric seas were advancing on all continents, reaching maximum extent during the Cenomanian. The resultant trend to widespread, more equable climate favored the invasion into the lowlands of angiosperms whose postulated origin was in mild uplands at low latitudes during pre-Cretaceous times. As tropical and subtropical lands were rafted farther apart by ocean-floor spreading following Albian-Cenomanian times, new taxa (species, genera, tribes, families) evolved in isolation. This accounts in part for the increasing richness of the three major tropical floras following the Cretaceous. Changes in Mesozoic paleogeography also appear to clarify several other puzzling aspects of early angiosperm history and distribution, including their early appearance at middle latitudes.