Cretaceous Angiosperms: Evolutionary, Geographical, and Paleoclimatic Aspects (on S.V. Meyen’s Scientific Legacy)

The additional arguments regarding the Cretaceous evolution of angiosperms are provided and further develop the evolutionary ideas proposed by S.V. Meyen. The quantity, diversity, and geographical distribution of angiosperms that first appeared at the beginning of the Cretaceous (Berriasian) increased considerably starting from the end of the Albian. The latter could be due to the fact that a hot humid equatorial belt appeared in the Albian for the first time in the Cretaceous history of the Earth and acted as a “generator of suprageneric taxa” of higher plants. An angiosperm macroevolution velocity increased dramatically owing to the development of this belt, while fluctuations in the Late Cretaceous climate launched the equatorial pump “at full capacity.” The anatomy of the Triassic bennettitalean microsporangium Leguminanthus is indicative of the fact that this gymnosperm group had a morphological structure that likely led to the formation of a closed (with closed margins) seed organ similar to the carpel of angiosperms, probably by means of a large evolutionarily significant saltation as gamoheterotopic transformation of female bennettite fruitifications to the anatomy of male ones. The presence of wide and probably flattened petioles and rachis in the Triassic bennettitalean Pterophyllum leaves confirms indirectly the validity of the assumption that angiosperm leaves could have evolved from those of bennettitaleans by means of phyllodization (flattening and enlargement of a leaf petiole).