Mesozoic plants and the problem of angiosperm ancestry

Abstract

Krassilov, V.: Mesozoic plants and the problem of angiosperm ancestry. Trends leading to the foliar and floral structures of angiosperms may be deduced by comparison with Mesozoic gymnosperms. The Debeya-Fontainea group of Cretaceous angiosperms closely resembles the Early Mesozoic Scoresbya group of pteridosperms with regard to leaf characters. The bivalved capsules of Jurassic Leptostrobus, with stigmatic bands, are regarded as the forerunners of certain types of angiosperm carpels. The angiospermous characters arose in several lineages of gymnosperms and were probably accumulated by non-sexual transfer of genetic material. The earliest angiosperm mega- and microfossils have been reported from the Middle and Upper Jurassic of the northern hemisphere. Most of these angiosperms were confined to chaparral-like communities dominated by shrubby conifers and cycadophytes. The rise of angiosperms was promoted by the climatic changes and the simultaneous rise of mammals.