Gondwana Flora

Classification of the Gondwanas: The classification of Indian Gondwanas is a matter of controversy. G. de Cotton (1917) and Fox (1931) divided the Gondwana system into two major divisions. Lower Gondwana (Lower Permian to Lower Triassic) and Upper Gondwana (M. Triassic to L. Cretaceous) which are characterised by Clossopteris and Ptilophyllum floras, respectively. Feistmantel (1876) and Vredenburg (1910) proposed a three-fold classification of Gondwana: Lower, Middle and Upper Gondwanas which are correspondingly equivalent to the Permian, Triassic and Jurassic. All the localities containing Lower Gondwana fossils, but bearing the lithological characteristics of the Upper Gondwanas such as Panchet, Pachmari, Parsona, Maleri etc. are retained in the Middle Gondwana. The Middle Gondwana is characterised by Dicroidium flora, present in between the Glossopteris and Ptilophyllum floras. Subsequently, most of the palaebotanists supported the three-fold division of Gondwana. The sub-divisions of Gondwana system are further divided into various series and stages. There is no controversy regarding the division of Gondwana up to series. However, the controversy arises at the level of stages and horizons. The flora of Gondwana is arranged with reference to the time scale which begins with the Talchir and extends up to the Bansa, Pariwar and Bhuj Formations. Lower Gondwana: This division shows predominance of the Glossopteris flora, during Permian period, in which the Talchir, Karkarbari, Barakar, Barren measures Raniganj, Motur, Hingir and Bijori Formations are included. Some elements of this division continues till the Middle Triassic. 1. Pteridophytes: (i) Equisetales : Schizoneura, Phyllotheca, Stellotheca. (ii) Sphenophyllales: Sphenophyllum, Rani- ganjia, Trizygia.

(iii) Lycopodiales : Cydodendron. (iv) Filicales : Gondwanidium, Pecopteris, Sphenopteris, Angiopteridium, etc. 2. Gymnosperms: (i) Glossopteridales : Gangamopteris, Glossopteris, Rubidgea, Rhabdotaenia, Vertebraria, Scutum, Ottokaria, Glosso- theca, etc. (ii) Cycadales: Pseudoctenis, Taeniopteris. (iii) Cordaitales : Noeggerathiopsis, Eury- phyllum, Cardiocarpus, Samaropsis. (iv) Ginkgoales : Psygmophyllum, Ginkgo- phyton. (v) Coniferales : Buriadia, Barakaria, Dadoxylon, Araucareoxylon, Agathoxylon, Damudoxylon etc. Middle Gondwana: This is characterised by the accession of Dicroidium and declining of Glossopteris flora (mixed flora) at the beginning of Triassic which extends up to the Upper Triassic with dominance of Dicroidium flora. In this division, Panchet, Kamthi, Pachmari, Maleri, Parsora, Bagra, Tiki, etc. Formations have been included. Pteridophytes: (i) Equisetales : Schizoneura. (ii) Calamitales : Neo-Calamites. (iii) Filicales : Pecopteris, Sphenopteris, Marianopteris Cladophlebis. 2. Gymnosperms: (i) Glossopteridales Dictyopteridium.

:

Glossopteris,

(ii) Corystospermales : Dicroidium. (iii) Cycadales: Pseudoctenis, Taeniopteris.

Macro-

taeniopteris,

Vertebraria,

(iv) Cycadeoidales : Pterophyllum, Zamites, Podozamites. (v) Cordaitales : Neoggerathiopsis, Cardio- carpus, Samaropsis. (vi) Coniferales : Araucarites.

Mid Gondwana flora Upper Gondwana This is characterised by the arrival of Ptilophyllum flora till the end of Gondwana era, ranging from Jurassic to Lower Cretaceous, in which Dubrajpur, Rajmahal, Kota, Jabalpur, Gangapur, Shivganga, Bhuj, Pariwar, etc., Formations are conveniently included. There is overlapping of the three distinct floras where the elements of the dying flora crawl for some time amongst the evolving flora, thus, showing the floral continuity throughout the Gondwana period. So, there is a gradual decline of one flora with the simultaneous evolution of the other, both in number of individuals and species. Even in a single flora, there is specific delimitation where certain species characterise the smaller units of bigger sub-divisions.

Lower Gondwana flora

Flora of upper Gondwana; 1. Pteridophytes: (i) Lycopodiales : Lycopodites. (ii) Isoetates : Isoetites. (iii) Equisetales: Equisetites. (iv) Filicales : Phlebopteris, Marattiopsis, Gleichenites, Sphenopteris, Osmundites, Cladophlebis, Cyclopteris. 2. Gymnosperms: (i) Corystospermales: Dicroidium, Pachypteris, Cycadopteris. (ii) Cycadales : Niissonia, Taeniopteris, Macrotaeniopteris, Pseudoctenis. (iii) Cycadeoidales : Pterophyllum, Ptilo- phyllum, Bucklandia Weltrichia, Zamites, Podozamites, Otozamites, Williamsonia, Cycadeoidea, Anomo- zamites, Sahnioxylon. (iv) Caytoniales : Sagenopteris, Caytonia, Caytonanthus. (v) Pentoxylales : Nipaniophyllum, Carnoconites, Pentoxylon. (vi) Cordaitales : Neoggerathiopsis, Cardio- carpus, Samaropsis. (vii) Coniferales : Dadoxylon, Stachyotaxus, Elatochadus, Nipaniostrobus, Sitholeya, Indophyllum, Pagiophyllum, Brachyo- phyllum, Araucarites. (viii) Ginkgoales : Baiera, Ginkgoites. (ix) Taxales : Taxaceoxylon, Torreyites, Taxites.

Upper Gondwana Flora