Studies in the Glossopteris Flora of India- 32. on The

STUDIES IN THE GLOSSOPTERIS FLORA OF INDIA 32. ON THE GENUS GANGAMOPTERIS McCOY P. K. MAITHY Birbal Sahni Jnstitute of Palaeobotany, Luckoow ABSTRACT 1902; WALKOM, 1922, 1938; TEICHERET, 1943), South Africa (SEWARD et al., 1908; The genus Crmgamopleris McCoy is an important constituent of the Glossopteris flora. Several views DU Ton, 1927, 1929; PLUMSTEAD, 1956, have been expressed in past for its specific de 1958), Belgian Congo (H4>EG & BosE, 1960), limitation but none of them have so far been proved Angola (KRISHNAN, 1960); Rhodesia & to be very satisfactory. In the present paper Nyassaland (LACEY, 1961); Brazil (WHITE, some suggestions are proposed for the specifIc delimitation of the genus on the basis of external 1908; CARRUTHERS, 1869; LUNDQUVIST, morphology of leaves. 1919; DOLJANITI, 1954a, b); Argentina (ARCHANGELSKY, 1957, 1958) and Antartica INTRODU~TION (PLUM STEAD, 1962). Some species of Ganga rnopteris have been described from Angara ANGAMOPTERIS McCoy is an im flora (ZALESSKY, 1918). The assignment portant member of the Glossopterideae. of these leaves to Gamgamopteris is not free G It was first described by McCoy (1847) from doubts, because so far the relationships from Australia. Since then a large number between the two flora, i.e. Angara flora of leaves have been assigned to it from and Glossopteris flora is not well established. various Lower Gondwana formations of Gangamopteris is probably the oldest the Southern hemisphere. In recent years member of the Glossopteris flora and in Srivastava (1956), H4>eg & Bose (1960) every country is first to appear, sometimes and Maithy (1965) have described the epi alone or with Glossoptertis. In comparison dermal structure. Gangarnopteris fructifica to its wide geographical distribution the tions have been described by Plumstead vertical range is limited, therefore, the (1960, 1963) from South Africa, viz. Otto genus is of considerable stratigraphical haria buriadica, Ottokaria transvaalensis and importance. The genus is more common Vannus gondwanensis. Ottokaria tYFe of in the Lower Permian and is rare or absent fructification are also known to be attached in the Upper Permian. In India Ganga to Glossopter·is indica. Plumstead (1958: mopter·is is dominant in Talchirs and 65) opined that Ottokaria may be the fructi Karharbaris, whereas in Damudas it is fication of both the genera, Gangamopteris represented by only one definite species. and Glossopteris. From Raniganj stage about six species of So far very little is known about the habit Gangamopteris are known but the identity and growth of Gangarnopteris. Some clusters of some seems doubtful. In Australia it of leaves belonging to G. obovata and G. has been recorded along with marine fossils indica were recorded from Wankie, South in the Lower Marine series about 2000 feet Rhodesia, by Plumstead (1958a) and on the above its base and it reaches to the maxi basis of these specimens, she concluded mum development in the Lower Series of that they were mainly deciduous, woody Coal Measures and gradually declines during plants of arborescent habit with leaves the Upper Coal Measures. In Africa it growing at short shoots, in clusters at fairly occurs both in the Dwyka and Ecca series wide i"ntervals from the woody stems. of the Karoo system and had been found by Leslie (1921) at Vereeninging below the DISTRIBUTION OF Dwyka Tillite. Above the Tillite' it is GANGAMOPTERIS is common in Middle Ecca, but not higher. It is found both in Brazil, Argentina and Gangamopteris is widely known from Antarctica from beds regarded as Lower India (FEISTMANTEL, 1879, 1881, 1882, Permian in age. 1886; SEWARD, 1907), Australia (FEIST Gangamopteris was first described by MANTEL, 1890a, b; McCoy, 1847; ARBER, McCoy (1847) from New South Wales as 46 MAITHY - STUDIES IN THE GLOSSOPTERIS FLORA OF INDIA - 32 47 Cyclopteris? angustifolia for a leaf showing doubtful whether the genus Gangamopteris netted venation as in Glossoptertis, but should not be merged in Glossopteris". This without a midrib. This specimen was referred has also been su pported by Wal kom (1922). to Cyclopten's with some hesitation by McCoy Surange & Srivastava (1956) favoured this but at the same time he thought that the view on the basis of the cuticular studies difference in the venation is of the generic and stated" it is thus evident that Glossop value. Later McCoy (1860) examined a teris, Gangamopteris and Paldeovittaria large number of specimens from the cannot be regarded as natural genera" Bacchus - Marsh Sandstone, Victoria and and supported further splitting of these came to the conclusion that the anastomo genera. However, the separate retention sing of viens and the absence of a midrib of Gangamopteris from Glossopteris seems are constant feature and hence, he proposed to be essential because in only few cases the generic name Gangamopteris. the specimens with a fructification or The original diagnosis given by McCoy cuticle are found. was later modified by Feistmantel (1879) In certain case the generic identificatIOn and Arber (1905)., In recent years the between Glossopteris and Gangamopteris epidermal structure has been described by becomes difficult. Several of the Glossop Srivastava (1956), H<jJeg & Bose (1960) and teris specimens with striations on their Maithy (1965). Thus, in view of the above midrib superficially appear to belong to addition to our knowledge the genus Ganga Gangamopteris. Therefore, one must take mopten's is redefined as below: due precaution for generic identification, "Leaves simple, entire. symmetrical or It must be worth while to mention here asymmetrical; linear, lanceolate, elli ptical, that most of the Gangamopteris species spathulate or obovate in shape; apex broadly described earlier from the Raniganj stage rounded, obtuse, acute, acuminate or seems to be Glossopteris. mucronate; base petiolate or contracted. Midrib absent; median region occupied by PROBLEM OF SPECIFIC DELIMITATION subparallel veins with anastomoses of elon gate or hexagonal outline. Secondary The leaves of Gangamopteris are known veins arise from median veins by repeated to be commonly preserved in the form of dichotomy, arched, bifurcating and anasto impressions and sometimes as compressions. mosing network." In the former case the study is limited to " Cuticle differentiated into two surfaces, externally recognizable characters of the stomata present on one or both the surfaces, impressions. While in the latter case, in stomatal apparatus haplocheilic, monocyclic, addition to the external morphological or dicyclic, distribution and orientation of study, there is a scope for cuticular study, stomata regular to irregular, papillae present Till a decade or two back the specific identi or absent." fication and comparison were in a large The genus Gangamopteris is closely allied majority of cases based solely on external to Glossopteris. Gangamopteris differs from features of the frond. In recent years the Glassopteris in that it has no midrib and general trend has largely shifted on the the veins are either radiating from lower epidermal studies and the results have median portion of the leaf or forming a proved that the epidermal structures are group of almost parallel anastomosing veins a more constant and reliable character for occupying the position of a midrib. In the proper identification and circumscrip past several workers have expressed doubts tion of a species. In this connection on the generic status of Gangamopteris, Sahni as early as 1923 (p. 277) has stated Seward (1910: 513) opined" the presence that .. a special advantage of such studies or absence of a midrib is not in itself a is that, once we have learnt to associate character of real taxonomic importance." certain epidermal character with certain Arber (1902) on the basis of the discovery species, it would thenceforth be easy to of 'Scale leaves' of Glossopteris expressed identify even small fragments which may his opinion "that the midrib is no longer otherwise be unrecognizable". It is gene a necessary characteristic of that genus" rally presumed that the leaves with similar and he further stated, .. it is, therefore, in morphological feature will yield one type the absence of full knowledge of the fructi of cuticles. But cuticular evidence of the fication of the either type, extremely Glossopteridean remains have shown that 48 THE PALAEOBOTANIST leaves resembling superficially differ in ported by Walkom (1922). The recent their epidermal structures, e.g. Glossopteris evidences of cuticular studies of Glossopteri indica Schimper-type of leaves have dae and related remains go against Arber's yielded three different types of cuticles, contention and support more to the liberal viz., Glossopteris indica Zeiller (1896). species concept of Feistmantel. The studies Glossopteris arberii Srivastava (1956) and of Lele & Maithy (1964) on the genus Glossopteris jamotii H<j>eg & Bose (1960). Neoggerathopsis has amply shown that the On the other hand leaves with different combination of the external morphological morphological features viz., Palaeovittaria features, i.e. Leaf shape, apex, base and kurzi and Glossoptfris intennittens have venations can more advantageously be used similar cuticles. Thus, these cuticular for specific delimitation. This has also been evidences leads us to the conclusion. that supported by the epidermal studies of these these homogenous looking leaves are hetero leaves. genous in nature and their number of species On the basis of the above evidences

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