J. Indian bot. Soc. e-ISSN:2455-7218, ISSN:0019 - 4468 Vol. 98 (3&4) 2019: 103-124 EARLY CRETACEOUS FERNS FROM INDIA- DIVERSITY, DISTRIBUTION AND THEIR RELATION TO THE MODERN FERNS CHINNAPPA CHOPPARAPU*, PAULINE K SABINA AND RAJANIKANTH ANNAMRAJU * Dept. of Botany (PG), Andhra Loyola College, Vijayawada, Andhra Pradesh, Birbal Sahni Institute of Palaeosciences, 53 University Road, Lucknow Email:[email protected] Date of online publication: 30th September 2019 DOI:10.5958/2455-7218.2019.00016.0 Ferns are a resilient group with a long fossil record. They were constituents of early terrestrial plant ecosystems and significantly diversified during the Early Cretaceous times. Indian Early Cretaceous sedimentary basins hold important fern relics belongs to the Equisetaceae, Marattiaceae, Osmundaceae, Gleicheniaceae, Dipteridaceae, Matoniaceae, Schizaeaceae, Marsileaceae, Cyatheaceae, Dicksoniaceae, Pteridaceae, Aspleniaceae, Dennstaedtiaceae, Dryopteridaceae and a few more taxa with unknown affinity placed under the miscellaneous ferns. With about 25 species, the Osmundaceae shows greatest taxonomic diversity among all the families. The taxonomic composition and distribution pattern of these fern families largely differ from basin to basin. These discrepancies are attributed to their functional ecology and taphonomy. The maximum numbers of families are reported from the Rajmahal Basin. Coastal sedimentary basins comparatively represented low diversity and usually contain Equisetaceae, Osmundaceae, Gleicheniaceae and Matoniaceae. Comparison of the early Cretaceous ferns with the recent ones connotes little relation between the two. The study suggests that the bulk of recent ferns were evolved during the post Cretaceous period. Key-Words: Diversity, Ferns, Early Cretaceous, Evolutionary History, India. The advent of terrestrial plant ecosystems 1996a). Presently there are about 300 extant during the Paleozoic era (480-360 Ma) was genera of ferns with 12,000 species widely marked by the first appearance of early land distributed throughout the world (Tidwell and plants (Banks 1968, Gray 1984, Edwards and Ash 1994, Smith et al. 2006). The greatest Fanning 1985, Selden and Edwards 1989, diversity occurs in the tropical regions and at Kenrick and Crane 1997). Plant communities high elevations (Tryon and Tryon 1982). Rich consisted chiefly of early cryptogamic fossil records also demonstrate their diversity vascular plants-Pteridophytes, which formed during the early Cretaceous (Surange 1966, bulk of coal forming vegetation (Thomas Sukh-Dev 1972, Vakhrameev 1991, Stewart 2012). Pteridophytes, the primitive vascular and Rothwell 1993, Cantrill 1998, Rothwell plants include the ferns (Filicatae) and related 1999, Cantrill & Nagalingum 2005, families Isoetaceae, Lycopodiaceae, Nagalingum and Cantrill 2006, Taylor et al. Psilotaceae and Selaginellaceae. Since the 2009). Although, ferns first appeared around group occupies a unique position between the 360 million years ago (Carboniferous), they lower cryptograms and higher vascular plants, attained modern affinity around 145 million their evolutionary status attracted many years ago during the early Cretaceous (Tidwell researchers (e.g. Surange 1966, Smith and and Ash 1994, Collinson 1996, Rothwell 1996, Breedlove 1981, Dixit 1984, Fraser-Jenkins Skog 2001, Soltis et al. 2002). The early 1986, Brownsey & Smith-Dodsworth 1989, Cretaceous period witnessed wide distribution Pryer et al. 2001, 2004, Schneider et al. 2004, of many fern groups forming the understorey in Rothwell and Stockey 2008, Christenhusz et forests (Gould 1975, Skog 2001, Van al. 2008, Taylor and Taylor 2009). Konijnenburg-van Cittert 2002, Chinnappa Interestingly ferns constitute nearly 90% of and Rajanikanth 2017). pteridophytic diversity. They are an extremely The Indian record of ferns dates back to the large and diverse group of modern land plants, Permian (Feistmantel 1879). However, only a second only to the angiosperms in the number few modern fern families such as Equisetaceae of extant species (Bierhorst 1971, Rothwell and Gleicheniaceae with extinct taxa are Received on July 02, 2019 www.indianbotsoc.org Accepted on July 22, 2019 Early Cretaceous ferns from India J. Indian bot. Soc.98 (3&4) 2019 :104 known during the Permian. The major art knowledge on early Cretaceous sequences radiation of the group in terms of taxonomic (McDougall and McElhinny 1970, and spatial diversity took place during the Rajanikanth et al. 2000). Mesozoic especially, during the early 2.RESULTS Cretaceous (Surange 1966). By this time many 2.1 Taxonomic diversity and Geographical modern fern families with taxa that can be distribution affiliated to recent ones started to appear. This 2.1.1. Equisetaceae trend was studiedly increased towards the Equisetaceae constitutes the only surviving tertiary period and by end of this period the lineage of the Sphenopsids (Scagel et al. 1984). group attained most of its modern affinity. The family for the first time appeared during Currently, the Indian extant ferns represented the Devonian (Stewart and Rothwell 1993). by 33 families and 125 genera with about 975 Existence of this family during the species (Fraser-Jenkins 2008). These are Carboniferous in the form of permineralized mostly distributed in Himalayan, North east remains (Coal ball) is well established (Taylor India and Southern India; only a few taxa e.g. et al. 2009). During the geological past, Equisetum, Asplenium, Osmunda etc. show equisetaleans were common both in wide geographic distribution. Gondwanan and Eurasian locales (Bose et al. The present communication constitutes a 1990, Vakhrameev 1991, Bomfleur et al. critical appraisal to the taxonomic diversity and 2013). An earliest reports of the family from geographical distribution of the early India were during the Permian (Feistmantel Cretaceous ferns from the Indian sub- 1879) and represented by Schizoneura, continent. Relation with the extant ferns and Neocalamites and Equisetites/Equisetum. evolutionary implications of these fossil ferns Among these three genera the former two were are also considered briefly. known from the sediments older than the Jurassic and the latter is know from younger 1.METHODS AND SOURCE OF DATA sediments (early Cretaceous) and extended to Indian early Cretaceous fossil fern data date. available in published literature (Sharma 1973, Fossil Equisetum has been described under the 1975, Lakhanpal et al. 1976, Banerji 1990, form genus Equisetites Sternberg by many 1993, 1995, 1995a, 1996, 2000, Pandya & authors around the world (e.g. Allen 1941, Sukh-Dev 1990, Singh et al. 1990, Chandra & Kon'no 1962, Bose & Banerji 1984, Sukh-Dev Tewari 1991, Patra & Sahoo 1992, Prakash & & Rajanikanth 1988). These were well Sukh-Dev 1995, Banerji & Jana 1998, 2000, preserved by stem, leaves, rhizomes and nodal Srivastava et al. 1999, 2005, Prakash 2000, diaphragms (Sahni & Rao 1933, Harris 1961). The fossil remains show apparent similarities 2003, Sharma et al. 2001, Banerji & Ghosh with living genus in its gross morphology, 2006, Pal et al. 2009, Chinnappa and except for its geological distribution and hence Rajanikanth 2017) has been compiled to it is preferable to use the extant name provide measures of diversity and distribution Equisetum L. (Harris 1961). In India, during pattern. The extant fern diversity and the early Cretaceous period, the family was distribution in India, has been recently represented by a single genus with three provided by Chandra (2000) and Fraser- species (Table 2). Geographically the family Jenkins (2008). The classification followed was widely distributed and it is reported from here is essentially of Smith et al. (2006). the Pranhita-Godavari, Cauvery, Mahanadi, Species assignments by original authors are Kutch, Rajasthan, Satpura and Rajmahal adhered with minor changes. The fossil taxa of basins (Oldham and Morris 1863, Feistmantel unknown affinity have been treated as 1876, Bose and Banerji 1984, Sukh-Dev and “Miscellaneous Ferns” (MS). Age assignments Rajanikanth 1988, Singh et al. 1990, Patra and for various litho-units are based on the state of Chinnappa Chopparapu, Pauline K Sabina and Rajanikanth Annamraju J. Indian bot. Soc.98 (3&4) 2019 :105 Figure 1: Distribution of Fern families in various early Cretaceous sedimentary basins of India. Sahoo 1992, See Fig. 1). Table 1: Showing the first appearance of various the fern The extant members of the family are families in India. represented by a single genus i.e. Equisetum with 15 species (Smith et al. 2006). These are Family Earliest fossil record distributed in almost all parts of the globe Equisetaceae Permian except Australia and New Zealand (Scagel Marattiaceae Triassic 1984, Husby 2013). With 4 species, the genus is Osmundaceae Triassic widely distributed throughout the Indian subcontinent (Fraser-Jenkins 2008). The Gleicheniaceae Permian family mostly grows in wet places such as Dipteridaceae early Cretaceous moist woods, ditches, stream/river banks, Matoniaceae early Cretaceous wetlands and in where sufficient ground water Schizeaceae early Cretaceous is available. The same is applies to the Marsileaceae early Cretaceous Cretaceous representatives as there is apparent morphological similarity. Cyatheaceae early Cretaceous 2.1.2. Marattiaceae Dicksoniaceae early Cretaceous Marattiaceae is a primitive leptosporangiate Dennstaedtiaceae early Cretaceous fern family dating back to the Paleozoic, about Pteridaceae early Cretaceous 345 million years ago. The family has a more