Pa/ambo/GI/il/ 49 (2000) 3.13-352 0031-0174/2000/333-352 $2.00 Taxonomy and diversity of the genus Glossopteris SHIV MOHAN SINGH* Birbal Salmi Il15titli/e of Palaeobotany, 5] Uni\'ersiry Road, LlicknOlv 226 007, India. Present address: TaxonolllY & Biodiversity Division, Narional Botanical Research Instirll/c, Rana Pratap Marg, LIICkl1o\v 226 001, Indic!. (Received 08 June 1999; revised version accepted 08 June 2000) ABSTRACT Singh SM 2000. Taxonomy and Diversity of the genus Glossopteris Palaeobotanist49(3) : 333-352_ The speciation of Glossopteris leaves in Permian Gondwana of India is re-examined. It is based on study of thousands of specimens collected from Barakar Formation of Karanpura and Bokaro Group of Coalfields. The study of specimens of modern plants showing variation in shape and size of leaves within same species (sometimes within same plant) and survey of published literature, the author was fascinated to express the ideas about the parameters which may be helpful in speciation of the genus Glossopteris. Here. morphological characters have been critically analysed in order to find a reasonable basis for precise spe­ cific delimitations. The morphological circumscriptions have been further verified by characters of cuticle which have been taken as associated or supportive characters only. The size and shape of leaves have given secondary importance. The Diversity and the total number of species found in time and space have been tabulated. Key·words- Glossopteris, Permian. Morphology. Cuticle. Speciation, Gondwana. India. 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SINGH- TAXONOMY AND DIVERSITY OF THE GENUS GLOSSOPTERIS )~5 INTRODUCTION is a genus of tongue-shaped fossil leaves which have a robust to flat midrib that gives off secondary veins that dichotomise Though the genus Glossopteris is the most abundant of and anastomose. The genus was first recognised by Adolphe all plants in the Permian floras, it has not been circumscribed Brongniart (1828), the father of Palaeobotany. He r~cognised in definite species within a genus. The main reason for this two species in the genus, viz., G. browniana var. allSlralisica was a complete lack of accepted criteria on which to base from Australia, G. browniana var. indica from India and G. such classification. The first attempt in this direction was made angustifolia also from India. Schimper (1869) raised var. by Arber (1905) whose system of specific circumscription has indica to the status of a species as G. indica. Dana (1849), been widely followed. In view of earlier researches on the Bunbury (1861) and Feistmantel (1876-1881, 1886, 1890) morphography and cuticular structure of leaves and on the described a number of species of Glossopteris from India nature of fructifications borne by these leaves; there is an and Australia. Zeiller (1896) reported for the first time the apparent lack of agreement between the two systems of epidermal structure of a leaf he identified as G. indica. The classification (Srivastava, 1957; Plumstead, 1958). Hence results of investigations in the genus done in the nineteenth there is a greater need for further work in this direction and century were summarised by Arber (1905). Though sporadic the evidences they obtained have to be correlated with those work continued in the early part of the twentieth century, the obtained by more critical studies on the fructification and the investigation got an impetus in the 1950s onwards when a lot cuticular structures. Though the evidences provided by the of data was generated not only on the morphography and cuticular and the fructifications are very important, their taxonomy of the leaves but also on the cuticular features and application is admittedly limited as most of the Lower attached/associated fructi fications. In spite of all this, there is Gondwana fossils occur more frequently as impressions. Hence still a controversy about the characters on which speciation in the natural thing is to device a classification based on the the genus should be based. Most workers prefelTed to separate morphographical characters. On the basis of morphography forms into different species on the basis of minor differences the retention of the taxonomic status of the present genus while others believed in maintaining a few species by merging Glossopteris seems to be most advisable and advantageous different forms of leaves into one, if most of the characters of inspite of the obvious di fficulties sometimes encountered in such leaves were the same. These two schools of speciation determination of transitional forms. It is hoped that ifdue care have been termed "splitters" and "Iumpers", respectively is taken in identifying the specimens described in the (Plumstead, 1962). Monograph of Chandra & Surange (1979), the cuticular Seward (1897, p. 317) believed that size and shape are species and the list of species given in Fig. I the most of the extremely dangerous guides in specific delimitation. Seward species will fit in one another and the number may become (1910) went to extent of suggesting that speciation based on half. In the Karanpura & Bokaro Coalfields the circumscription venation and generic delimitation on the basis of presence or of species made by studying more than one specimens and absence of a midrib is not justified. Earlier Arber (1905), a intensi ve observations have gi ven 32 species (Thesis Shi v strong supporter of maintaining a few species only, re-classified Mohan Singh, Contributions to the Early Permian flora of species distinguished by earlier workers into thirteen species Karanpura and Bokaro Coalfields, 1998). only. According to him "there existed a considerable variation in the form and shape of the leaf of the genus Glossopteris SYSTEMATICS and in the details of the nervation, even in the fronds in which there is reason to believe belonged to the same plant". He did Genus-GLOSSOPTERIS Brongniart 1828 not take into account the characters of midrib, nature of apex and angle of divergence of secondary veins from the midrib Type species-GLOSSOPTERIS BROWNIANA as characters suitable for specific delimitation. He did think Brongniart 1828 that the only constant character for speciation was the open­ Glossopteris is the most abundant fossil in the Permian ness or close-ness of the secondary veins and hence the shape floras of the Southern Hemisphere, that during the period of meshes. However, Maheshwari (1966) opined that without comprised Australia, Antarctica, Africa, South America, and knowing the whole plant. it was not possible to know whether India, and possibly also the Arabian Peninsula. Glossopteris there was such a variation in the same plant or even in the /" " PLATE 1 I. Glossopteris karanpurael/sis Kulkarni 1971, Specimen no. BSIP­ 2-5. CUlicle of Glossopteris karanpurael/sis, probably of the slomatiferous 38836-13 (1/4578 A I). Barakar Formation, shales associated with surface. showing barely discernible laleral cell walls. and spindle­ Naditoli Seam. Sirka Colliery. South Karanpura Coalfield, Bihar. x shaped Slomala. Specimen no. BSIP-38836-B ( 1/4578 AI). 2 x 200. nat. size. 3·5 x 400. --J I en ..._v 'i:I r» t- en ;l> 0 -3 c:; 0 tr1 --J N » Z VJ --J SINGH- TAXONOMY AND DIVERSITY OF THE GENUS GLOSSOPTERIS l37 same species of fossi Ileaves. He pointed out that in a character, leaf may be assigned to Gangalllopteris. Besides Pant and co­ the delimitation of its range is difficult and so the variation workers, H0eg and Bose (1960). Surange and Maheshwari shall necessarily be an arbitrary one. (1962). Saksena (1963), Rigby (1966). Srivastava (1969. Before 1956 the speciation of Glossopteris was based 197/). Banerjee (1971), Chandra and Surange (1~77a, b). on morphography, i.e .. external features of the leaf. Zeiller Rigby et al., (1980), Chandra and Snvastava (1981) and (1896) and Sahni (1923) described the epidermal and cuticular Maheshwari and Tewari (1992) have reported on the cuticles structures of the leaves of G. indica Schimper and G. of Glossopteris leaves. angustifolia Brongniart, respectively. Srivastava (1957) made The first Glossopteris fructification was described and an effort to delimit species on the basis of cuticular characters. ill ustrated by Feistmantel (1881). Though the lectotypes for He described features of the cuticle in 16 species of the taxon Dict)'opteridiwlI sporiferulll (Geological Survey of Glossopteris, 6 species of Gallgalllopteris and one species of India, Calcutta, Museum Specimen 5210 figured by Banerjee Palaeovittaria. Surange and Sri vastava (1957) classified these 1973) does provide some evidence of probable attachment to 23 species in six groups on the basis of totality of cuticular a Glossopteris leaf. Feistmantel thought it was a fern plllnule. features. They thought that these groups could be of generic Zei lIer (1902) reported Ottokaria (Feistll/{/ntelia) bel1galensis rank.