Late Palaeozoic and Triassic floras of India and their relation to the floras of Northern and Southern Hemisphere

Abstract

The development, composition and phytogeographical distribution of the northern and southern hemisphere floras horn the Carboniferous to the Triassic times is critically reviewed in the light of more recent knowledge and with particular reference to India and other Gondwana countries. The Lower Carboniferous floras of Gondwanaland, and especially of India, are much impoverished in contrast to the Euramerian Lepidodendropsis flora. It seems more reasonable that the southern flora evolved from pre-existing Devonian stocks on ice-free areas of Gondwanaland whereas the Glossopteris flora arose under the impact of Carbo-Permian glaciation. Most of the so-called Euramerian elements in the Glossopteris flora (e.g. ferns, lycopods) may well be of southern nativity. Several of them are now proved to be distinct; the remaining few, obviously, warrant critical study.
 The Gondwana, Angara, Euramerian and Cathaysian floras and their respective palaeoenvironments had attained sharp geobotanical distinction in the Permian. Floral migration or contact between them across the Tethys is discussed. Particular attention is drawn to the phytogeographic significance of the Kashmir site (Gangamopteris beds) in the light of its geotectonic background and the recent findings of several extra-Gondwana (Cathaysian/Angara?) plants. The Kashmir site is here referred to Vakhrameev's " Middle Asiatic floras of uncertain affinity" which also includes the Hazro locality of Turkey. The Middle Asiatic region needs extensive palaeobotanical exploration to understand the nature of the maritime (Tethyan) floras of the various Permian geobotanical provinces.
 During the Triassic, the floral picture of the northern hemisphere became almost cosmopolitan following the withdrawl of previous physico-geographic barriers. The southern hemisphere (Gondwana) floras also tended to become more harmonious but their essential distinctiveness was still maintained by the characteristic prevalence of the Dicroidium flora.