Morphological Evolution of Indian Gondwana Megaspores

Abstract

The occurrence of abundant dispersed fossil megaspores in the Indian Gondwana sediments indicates the presence of heterosporous early lycopsid plants which are themselves uncommon. Study of megaspores is, hence, significant since it reflects on the evolution of early land plants. A variety of megaspores are recorded from various Gondwana basins of India. They are categorised on the basis of their shape, presence and absence of tri-radiate ridges and nature of exosporium and mesosporium. On the basis of their structural diversity, Permian megaspores show a distinct evolutionary trend. However, in the Mesozoic, no such trend is observed, probably because of paucity of megaspore records and also lack of complete information on mesosporium characters. A careful, detailed and comprehensive study is, therefore, required for a better understanding of the evolutionary trend of Mesozoic megaspores.