Turkish Journal of Botany Turk J Bot (2014) 38: 453-464 http://journals.tubitak.gov.tr/botany/ © TÜBİTAK Research Article doi:10.3906/bot-1308-35

New lauraceous species from the Siwalik forest of Arunachal Pradesh, eastern Himalaya, and their palaeoclimatic and palaeogeographic implications

Mahasin Ali KHAN, Subir BERA* Centre of Advanced Study, Department of Botany, University of Calcutta, Kolkata, India

Received: 20.08.2013 Accepted: 18.01.2014 Published Online: 31.03.2014 Printed: 30.04.2014

Abstract: Leaf remains of 4 lauraceous taxa collected from the Siwalik sediments (Middle Miocene to Pliocene) of Arunachal Pradesh of eastern Himalaya are described in the present communication. One fossil leaf, Cinnamomum palaeobejolghota sp. nov., was recovered from the lower part of the Siwalik succession (Dafla Formation; Middle to Upper Miocene), while mioparviflora sp. nov., Persea preglaucescens sp. nov., and Lindera neobifaria sp. nov. were collected from the middle part of the Siwalik succession (Subansiri Formation; Pliocene) of Arunachal sub-Himalaya. The geographic distribution of the fossils and their modern counterparts is discussed and on that basis tropical vegetation under warm and humid climate during deposition of the Siwalik sediments is suggested. The present study also suggests probable migration of these lauraceous taxa in South-East Asia.

Key words: Fossil, lauraceous leaves, Middle Miocene-Pliocene, new species, Siwalik, palaeoclimate, Arunachal Pradesh

1. Introduction Among the remains, 4 lauraceous leaves described in Juss. is a relatively primal family of angiosperms the present communication resembling modern Lindera widely distributed in tropical and subtropical warm bifaria (Nees) Benth. ex Hook. f., Persea parviflora Spreng., climate regions of South-East Asia and South America Persea glaucescens (Nees) D.G.Long, and Cinnamomum (Cronquist, 1981). It is one of the largest subtropical to bejolghota (Buch.-Ham.) Sweet were recovered from tropical families of woody , with over 50 genera and the road-cutting sections of the middle part (Subansiri 2500 to 3000 species (Rohwer, 1993). Formation: Pliocene) and lower part (Dafla Formation: Leaves of fossil members of the family Lauraceae are Middle-Upper Miocene) of the Siwalik strata in the West frequently found in the Tertiary deposits of India (Table Kameng District (27°16′14.2428″N, 92°24′4.0026″E) 1). The occurrence of laurels in fossil floras is significant (Figure 1). These fossil leaves are described here for the from a palaeovegetational, palaeogeographical, and first time from the Cenozoic sediments of India. The palaeoclimatic point of view. From the Siwalik strata present paper also discusses their phytogeographical and (Middle Miocene-Lower Pleistocene) of India, Lauraceae palaeoclimatic significance. leaves were reported frequently (Pathak, 1969; Lakhanpal and Guleria, 1978; Mathur, 1978; Lakhanpal and Awasthi, 2. Materials and methods 1984; Awasthi and Lakhanpal, 1990; Antal and Awasthi, The present study is based on 4 specimens, which are 1993; Prasad, 1994; Mathur et al., 1996; Shashi et al., 2008; satisfactorily preserved. The specimens were first cleared Srivastava and Mehrotra, 2009; Khan et al., 2011). with the help of a chisel and hammer and then their During palaeobotanical fieldwork, rich and diverse photographs were taken using a digital camera (Canon types of fossil plant remains including carbonised remains PowerShot A720IS). The external morphology of fossil of stems, leaves, seeds, and fruits were recovered from the leaves was studied with a hand lens and incident light Siwalik (Middle Miocene-Lower Pleistocene) sediments compound microscope (Stemi SV 11, Zeiss). Identifications exposed along the road- and river-cutting sections were made by comparison with modern lauraceous leaves in different districts of Arunachal Pradesh (situated collected from forests adjacent to the fossil exposures, as between 26°27′52″N and 29°29′54″N and 91°29′50″E well as with herbarium sheets of modern lauraceous taxa and 97°24′56″E). It is one of the north-eastern provinces kept in the Central National Herbarium (CAL), Sibpur, of India, bordering Tibet, Bhutan, China, and Myanmar. Howrah, West Bengal. The terminologies adopted by * Correspondence: [email protected] 453 KHAN and BERA / Turk J Bot

Table 1. Earlier fossil records of Lauraceae from India.

Fossil taxa Modern counterparts Locality Age References

Cinnamomum C. tamala Nees Darjelling Pliocene Pathak (1969)

Cinnamomum eokachchhensis Cinnamomum sp. Gujrat Eocene Lakhanpal and Guleria (1981)

Cinnamomum palaeotamala C. tamala Nees Bihar Miocene Lakhanpal and Awasthi (1984)

Kerala Miocene Awasthi and Srivastava (1992) Cinnamomum sp. Cinnamomum sp. Darjeeling Miocene-Pliocene Antal and Awasthi (1993)

Cinnamomum nepalensis C. caudatum Nees Uttaranchal Miocene Shashi et al. (2008)

Cinnamomum miotavoyanum C. tavoyanum Meisn. Uttaranchal Miocene Shashi et al. (2008)

Persea Persea sp. Kashmir Pleistocene Puri (1949)

Persea villosa Persea sp. Darjeeling Pliocene Pathak (1969) Persea odoratissima (Nees) Persea punyagiriensis Uttaranchal Miocene Lakhanpal and Guleria (1978) Kosterm. Persea lakhanpalii Persea lanceolata Nees Himachal Pradesh Oligocene Mathur et al. (1996)

Persea sibdasii Persea lanceolata Nees Himachal Pradesh Miocene Mathur et al. (1996)

Darjeeling Miocene Antal and Awasthi (1993) Actinodaphne palaeoangustifolia A. angustifolia Nees Arunachal Pradesh Plio-Pleistocene Khan et al. (2011)

Actinodaphne cf. obovata A. obovata Blume Arunachal Pradesh Plio-Pleistocene Khan et al. (2011)

Actinodaphne palaeomalabarica A. malabarica Balakr. Arunachal Pradesh Miocene Srivastava and Mehrotra (2009)

Lindera cf. pulcherrima L. pulcherrima Benth. Arunachal Pradesh Plio-Pleistocene Khan et al. (2011)

Michilus Michilus sp. Darjelling Pliocene Pathak (1969)

Michilus miocenica M. odoratissima Nees Uttaranchal Miocene Prasad (1994)

Machilus neyveliensis Machilus sp. Tamil Nadu Miocene Agarwal (2002)

Litsea L. polyantha Juss. Darjelling Pliocene Pathak (1969)

Litsea bhatiai Litsea consimilis Nees Himachal Pradesh Pleistocene Mathur (1978)

Litsea prenitida Litsea nitida Nees Bihar Miocene Lakhanpal and Awasthi (1984)

Litsea sastryi Litsea citrata Blume Himachal Pradesh Miocene Mathur et al. (1996)

Litsea Litsea sp. Rajasthan Plio-Pleistocene Mathur and Mathur (1998) L. glabrata (Wall ex Nees) Litsea preglabrata Arunachal Pradesh Miocene Srivastava and Mehrotra (2009) Hooker f. Litsea cf. salicifolia L. salicifolia Roxb. Arunachal Pradesh Plio-Pleistocene Khan et al. (2011) Nangwalbibra, North- Phoebe sublanceolata Phoebe lanceolata Nees Palaeocene Bhattacharyya (1983) East India Phoebe champarensis Phoebe lanceolata Nees Bihar Miocene Awasthi and Lakhanpal (1990)

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Dilcher (1974) were followed for description of the fossil leaves. All the specimens are kept in the Herbarium cum Museum of the Department of Botany, University of Calcutta (CUH). 2.1. Geology The Siwalik sediments lie along the foothills of Arunachal Pradesh and are subdivided into the Lower Siwalik (Dafla Formation, Middle to Upper Miocene), Middle Siwalik (Subansiri Formation; Pliocene), and Upper Siwalik (Kimin Formation, Upper Pliocene to Lower Pleistocene) as exposed in reverse stratigraphic order (Kumar, 1997). The northern limit of the Siwalik group is defined by the Main Boundary Fault, separating it from the pre-Tertiary sequence, while in the south the Brahmaputra Alluvium of the Brahmaputra Plain defines its boundary. The Main Frontal Thrust separates Siwalik sediments from the Quaternary Assam Alluvium (after Joshi et al., 2003). At places the contacts between the Lower and Middle and the Middle and Upper Siwalik are also tectonised and faulted (Table 2). The middle part of the Siwalik strata is characterised by medium- to fine-grained sandstones and siltstones, locally interbanded with carbonaceous shale and also containing bright fragments of coal/coalified woods. In comparison to the Lower Siwalik, the rocks are more friable and loose. Coarse-grained sandstones at the base Figure 1. Location of study area in West Kameng district, are successively overlain by greenish yellow siltstones with Arunachal Pradesh and a geological setting of the area around profuse ichnofossils, greenish yellow silty splintery shale, Bhalukpong and Pinjoli. grey silty shale with mud cracks, ripple marks, onion-skin

Table 2. Generalised lithotectonic sequence in the West Kameng District, Arunachal Pradesh (after Joshi et al., 2003).

North

Gondwana Group Carbonaceous shale, sandstone and coal

……….Main Boundary Faults………… Well-indurated sandstone, shale, and Lower Siwalik (Dafla Formation) siltstone with plant fossils ……………..Thrust…………………… Weakly indurated sandstone, shale, and Middle Siwalik (Subansiri Formation) siltstone with plant fossils ………………..Thrust…………………. Sand rock and claystone/shale with plant Upper Siwalik (Kimin Formation) fossils, fossil wood …………Main Frontal Fault………….

Assam Alluvium/ Quaternary deposits

South

455 KHAN and BERA / Turk J Bot like weathering features, friable yellow-coloured fractures, Description: Leaf simple, asymmetrical, elliptic; and silty shale with plant fossils (Figure 2). The lower preserved maximum lamina length 4.5 cm and maximum part of the Siwalik strata is represented by interbanded width 2.1 cm; apex acuminate; base asymmetrical, acute; medium- to fine-grained sandstones and shale containing margin entire; texture chartaceous; petiole missing; lenses/fragments of woody materials and lignitic coal. venation pinnate, eucamptodromous; primary vein The shale fraction locally contains plant fossils. The rocks (1º) single, stout, more or less straight; secondary veins are in general compacting, hard, indurated, sheared, seemingly 4 pairs preserved, 0.2 cm to 1 cm apart, alternate, and slickensided (Figure 2). Recently, on the basis of basal secondaries more acute than upper secondaries, magnetostratigraphic data, Chirouze et al. (2012) proposed secondary veins (2º) uniformly curved up, unbranched, that the Siwalik Formation in the Kameng section of angle of divergence acute, moderate, 50°–60°; tertiary Arunachal Pradesh was deposited between 13 and 2.5 Ma. veins (3º) poorly preserved, angle of origin nearly RR, The transition between the Lower and Middle Siwaliks is percurrent, oblique in relation to midvein. dated at about 10.5 Ma and the Middle to Upper Siwaliks Materials: There are 2 well-preserved leaf impressions, transition is dated at 2.6 Ma. the first is complete and the other is without the basal part. Type: Road section, Bhalukpong area, opposite from 3. Results Jangchip Chorten of West Kameng District, Arunachal 3.1 Systematic description Pradesh (Holotype: Specimen no. CUH/PPL/B/21). Same Order: Juss. ex Bercht. & J.Presl. locality; (Paratypes: CUH/PPL/B/21a; CUH/PPL/B/21b). Family: Lauraceae Juss. Stratigraphic horizon: Middle part of the Siwalik Genus: Lindera Thunb. succession of sediments (Subansiri Formation). Lindera neobifaria Khan & Bera sp. nov. (Figure 3). Age: Pliocene. Diagnosis: Asymmetrical, elliptic; lamina length 4.5 Etymology: Adding the prefix ‘neo’ to the modern cm and width 2.1 cm; base asymmetrical, acute; entire comparable specific epithet bifaria. margin; eucamptodromous venation; angle of divergence Remarks: In order to compare and find the nearest of secondary veins acute; tertiary veins RR, percurrent. generic affinity of the present fossil leaf, several modern

Figure 2. a- Lithological column for part of exposed road-section, Bhalukpong, opposite Jangchip Chorten (middle part of the Siwalik strata), b- lithological column for part of exposed road-section along Bhalukpong-Pinjoli road near culvert no. 48/1 (lower part of the Siwalik strata).

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bifurcated secondary veins. Furthermore, leaves of these modern species are mostly longer and narrower than the fossil leaf. One species of Persea viz., P. macrantha (Nees) Kosterm., also shows good resemblance to the fossil specimen, but it differs in having almost double the number of secondaries. The above-mentioned diagnostic features of the present fossil leaf indicate close resemblance of the fossil leaf to the modern genus Lindera Thunb. of the family Lauraceae. Herbarium sheets of the available modern species of this genus were critically examined and it was found that only 2 species, Lindera bifaria (Nees) Benth. ex Hook. f. and Lindera pulcherrima, are close to the fossil. In L. pulcherrima, the secondary veins are relatively more widely spaced and the apex is comparatively more attenuate than in the fossil specimen. Curvature of secondaries is also dissimilar. The leaves of L. bifaria show closer similarity to the fossil leaf in size, shape, and venation pattern (Figure 3). Earlier, a fossil leaf resembling the genus Lindera Thunb. was reported by Khan et al. (2011) from the upper part of the Siwalik sediments of Itanagar area in the Papumpare District of Arunachal Pradesh under the fossil species Lindera cf. pulcherrima. The present fossil leaf has been compared with the above known species and it was found that it differs from Lindera cf. pulcherrima (Khan et al., 2011) in having eucamptodromous venation as compared to the camptodromous-brochidodromous venation pattern in earlier reported species. On the basis Figure 3. Lindera leaves. a- Fossil leaf of Lindera neobifaria of such differences, it has been described as a new species, showing apex (black arrow), shape, size, and venation pattern; Lindera neobifaria Khan & Bera sp. nov. b- modern leaf of Lindera bifaria showing apex (black arrow), Genus: Persea Mill. similar shape, size, and venation pattern; c- enlarged portion Persea mioparviflora Khan & Bera sp. nov. (Figure 4). of the fossil leaf of Lindera neobifaria showing primary vein (red arrow), secondary vein (yellow arrow), and tertiary vein Diagnosis: Narrow elliptic shape; length 7 cm, width 1.5 (blue arrow); d- enlarged portion of the modern leaf of Lindera cm; apex and base acute; entire margin; eucamptodromous bifaria showing similar primary vein (red arrow), secondary vein venation; angle of divergence of secondary veins acute to (yellow arrow), and tertiary vein (blue arrow). Scale bar = 1 cm. right angle; absence of intersecondary veins. Description: Leaf symmetrical, simple, very narrowly elliptic; preserved lamina length 7 cm, maximum width 1.5 genera of Lauraceae were examined. The fossil specimen cm; apex seemingly acute; base wide acute; margin entire; shows resemblance to the extant leaves of some genera texture coriaceous; venation pinnate, eucamptodromous; of this family such as Actinodaphne Nees, Litsea Lamk., primary vein (1º) single, prominent, straight, slightly Persea Mill., and Lindera Thunb. Among the species of curved at the basal portion, thicker towards the base; Actinodaphne, A. angustifolia Nees and A. hirsuta Blume secondary veins (2º) only 4 pairs visible, 0.7 to 1.2 cm show fairly good resemblance to the fossil leaf, but A. apart, curved up, angle of divergence acute to right angle angustifolia differs in being larger in size, and the latter (60°–80°), alternate to opposite, unbranched, thinner species differs in having comparatively more attenuate towards the margin; intersecondary veins absent; tertiary apex. The secondary veins in A. angustifolia towards the veins (3º) not preserved. apical part are comparatively more sparsely arranged. On Material: There is a single satisfactorily preserved the other hand, secondaries in A. hirsuta are relatively specimen. more densely arranged. Leaves of Litsea sebifera Pers. Type: Road section, Bhalukpong area, opposite from and Litsea salicifolia (Roxburgh ex Nees) Hook f. show Jangchip Chorten of West Kameng District, Arunachal close similarity with the fossil, but they differ in having Pradesh (Holotype: Specimen no. CUH/PPL/B/20).

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On critical examination it was found that the fossil shows better resemblance to the leaves of Persea. Only 5 species of Persea are close to the fossil: P. parviflora Spreng., P. duthiei (King ex. Hook. f.) Kosterm., P. odoratissima (Nees) Kosterm., P. kingii (Hook. f.) Kosterm., and P. gamblei (King ex. Hook. f.) Kosterm. In P. duthiei, P. odoratissima, P. kingii, and P. gamblei the apex is acuminate, whereas in the fossil specimen it is acute. Furthermore, secondary veins in these species of Persea are comparatively more densely arranged. On the basis of leaf morphology (size, shape, nature of apex and base, texture, and venation pattern), P. parviflora shows the closest resemblance to the fossil specimen (Figure 4). So far, 5 fossil leaves resembling the genus Persea Mill. are known from the Indian subcontinent. These are Persea (Machilus) villosa (Pathak, 1969), Persea (Machilus) sp. (Puri, 1949), Persea puryagiriensis (Lakhanpal and Guleria, 1978), Persea lakhanpalii (Mathur et al., 1996), and Persea sibdasii (Mathur et al., 1996). The first 3 fossil specimens are incomplete and differ from Persea lakhanpalii and Persea sibdasii. The last 2 specimens resemble modern Persea lanceolata Nees in lanceolate shape of the lamina, craspedodromous venation, acute base, apex, and secondaries. However, our fossil specimen is distinct from the above-described fossil specimens and closely resembles the extant Persea parviflora Spreng. in its very narrow elliptic shape, eucamptodromous venation, Figure 4. Lindera leaves. a- Fossil leaf of Lindera mioparviflora and wide acute base. As the present fossil leaf is distinct showing shape, size, base (marked by black arrow), and venation from the earlier described fossil specimens, a new species, pattern; b- modern leaf of Persea parviflora showing similar Persea mioparviflora Khan & Bera sp. nov., is suggested. shape, size, base (marked by black arrow), and venation pattern; Genus: Persea Mill. c- enlarged portion of the fossil leaf of Lindera mioparviflora Persea preglaucescens Khan & Bera sp. nov. (Figure 5). showing primary vein (red arrow) and secondary vein (yellow Diagnosis: Narrowly elliptic; lamina length arrow); d- enlarged portion of the modern leaf of Persea parviflora 3.2 cm, width 1.9 cm; base acute; margin entire; showing similar primary vein (red arrow) and secondary vein eucamptodromous; angle of divergence of secondary veins (yellow arrow). Scale bar = 1 cm. acute; intersecondary veins present; tertiary veins fine with an angle of origin RR and percurrent. Stratigraphic horizon: Middle part of the Siwalik Description: Leaf simple, symmetrical, simple, narrow succession of sediments (Subansiri Formation). elliptic; preserved lamina length 3.2 cm, maximum width Age: Pliocene. 1.9 cm; apex broken; base acute; margin entire; texture Etymology: Adding the prefix ‘mio’ to the modern coriaceous; venation pinnate, eucamptodromous; primary comparable specific epithet parviflora. vein (1º) single, prominent, straight, slightly curved, thicker Remarks: The fossil specimen shows a resemblance to in the basal portion than in the middle and upper portion; the extant leaves of 3 genera of Lauraceae, Phoebe Nees, secondary veins (2º) only 4 pairs visible, 0.5 to 0.9 cm apart, Litsea Lamk., and Persea Mill. Leaves of some species of uniformly curved up, angle of divergence acute, narrow Phoebe show fairly good resemblance to the fossil leaf, but to moderate (40°–60°), alternate-opposite, unbranched; the secondaries in Phoebe run more or less straight towards intersecondary veins present; tertiary veins (3º) fine with the margin and in the fossil specimen they are more an angle of origin RR, percurrent, branched, alternate to curved. Furthermore, the leaves in Phoebe are relatively opposite, oblique in relation to midvein and close. thicker and coriaceous. Three species of Litsea, L. umbrosa Material: The species is based on a single, well- Nees, L. stocksii Hook. f., and L. glabrata Hook. f., show preserved, almost complete leaf impression. general similarity with the fossil, but in these species, the Type: Road section, Bhalukpong area, opposite from leaves are relatively smaller. Secondary veins of the latter 2 Jangchip Chorten of West Kameng District, Arunachal modern species are comparatively more densely arranged. Pradesh (Holotype: Specimen no. CUH/PPL/B/19).

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fructifera Kosterm., and P. gamblei (King ex Hook. f.) Kosterm., are comparable to the fossil specimen. Leaves of P. fructifera are longer and narrower than the fossil leaf. Moreover, secondary veins are bifurcated towards the margin. Leaves of P. gamblei attain a lanceolate shape in contrast to the narrow elliptic shape in the present fossil specimen. Besides, the secondaries are comparatively more widely spaced. The fossil specimen thus shows closest resemblance to the modern leaves of Persea glaucescens in size, shape, and vein architecture (Figure 5). Among the fossil leaves of Persea from the Indian subcontinent, 3 specimens, Persea (Machilus) villosa (Pathak, 1969), Persea (Machilus) sp. (Puri, 1949), and Persea puryagiriensis (Lakhanpal and Guleria, 1978), are incomplete and their photographs are not very clear. It is thus not possible to compare these specimens with the present fossil specimen. Two other earlier reported specimens, Persea lakhanpalii (Mathur et al., 1996) and Persea sibdasii (Mathur et al., 1996), differ in having lanceolate shape of the lamina in contrast to the narrow elliptic shape of the fossil leaf. Moreover, venation pattern of both specimens is of the craspedodromous type, while venation pattern of the present fossil is of the eucamptodromous type. As our fossil specimen is distinct from the earlier reported fossil specimens of Persea in size, shape, and venation pattern, a new species, Persea Figure 5. Persea leaves. a- Fossil leaf of Persea preglaucescens preglaucescens Khan & Bera sp. nov., is suggested. showing shape, size, and venation pattern; b- modern leaf of Persea Genus: Cinnamomum Schaeffer glaucescens showing similar shape, size, and venation pattern; Cinnamomum palaeobejolghota Khan & Bera sp. nov. c- enlarged portion of the fossil leaf of Persea preglaucescens showing acute base (black arrow), primary vein (red arrow), (Figures 6 and 7). secondary vein (yellow arrow), and tertiary veins (blue arrows); Diagnosis: Narrowly oblong; length 10.08–11.50 cm d- enlarged portion of the modern leaf of Persea glaucescens and maximum breadth 3.6–4 cm; acute base; margin showing similar nature of base (black arrow), primary vein (red entire; venation basal acrodromous, secondary veins arrow), secondary vein (yellow arrow), and tertiary vein (blue running approximately at right angles to acute angles, arrow). Scale bar = 1 cm. intramarginal veins present. Description: Leaf simple, symmetrical, obovate, Stratigraphic horizon: Middle part of the Siwalik narrow oblong; preserved maximum length 10.08–11.50 succession of sediments (Subansiri Formation). cm and maximum breadth 3.6–4 cm; apex broken; base Age: Pliocene. acute; margin entire; texture coriaceous; venation basal Etymology: Adding the prefix ‘pre’ to the modern acrodromous, perfect; primary vein (1º) 3, stout, almost comparable specific epithet glaucescens. straight, 2 lateral primaries slightly curved, unbranched; Remarks: Size, shape, texture, and venation pattern secondary veins (2º) fine, running approximately at right strongly indicate that the present fossil shows closest angles to acute angles, sometimes branched, arising from affinity with the extant leaves of Persea. Comparisons the median primary and joining the 2 laterals, also arising were also made with the leaves of other 2 genera of the from the outer side of the 2 lateral primaries at acute angle family Lauraceae, Litsea Lamk. and Persea Mill., showing and moving upward and forming the intramarginal veins; apparent similarity with the fossil. Two species of Litsea, tertiary veins (3º) with angle of origin RR, percurrent, Litsea monopeltata (Roxb.) Pers. and Litsea tomentosa unbranched, relationship to midvein at right angles, Heyne, show similarity with the fossil, but in both of them opposite; further venation details not observed. the leaves are comparatively larger. Materials: There are 7 well-preserved specimens; 3 are On thorough examination it was found that only almost complete, and some specimens are incomplete, 3 species of Persea, P. glaucescens (Nees) D.G.Long, P. containing only the basal portion.

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Figure 7. Cinnamomum leaves. a- Enlarged portion of the fossil leaf of Cinnamomum palaeobejolghota showing median primary vein (red arrow), lateral primary vein (yellow arrow), secondary Figure 6. Cinnamomum leaves. a- Fossil leaf of Cinnamomum vein (blue arrow), and branched secondary vein (white arrow); b- palaeobejolghota showing base, shape, size, and venation pattern; enlarged portion of the modern leaf of Cinnamomum bejolghota b- modern leaf of Cinnamomum bejolghota showing similar base, showing similar median primary vein (red arrow), lateral primary shape, size, and venation pattern; c- enlarged portion of the fossil vein (yellow arrow), secondary vein (blue arrow), and branched leaf of Cinnamomum palaeobejolghota showing median primary secondary vein (white arrow); c- enlarged basal portion of the vein (red arrow), lateral primary vein (yellow arrow), secondary fossil leaf of Cinnamomum palaeobejolghota showing median vein (blue arrow), and tertiary vein (green arrow); d- enlarged primary vein (red arrow), lateral primary veins (yellow arrows), portion of the modern leaf of Cinnamomum bejolghota showing and basal portion of primary vein (white arrow); d- enlarged similar median primary vein (red arrow), lateral primary vein basal portion of the modern leaf showing median primary vein (yellow arrow), secondary vein (blue arrow), and tertiary vein (red arrow), lateral primary veins (yellow arrows), and basal (green arrow). Scale bar = 1 cm. portion of primary vein (white arrow). Scale bar = 1 cm.

Type: Road-cutting section along East Pinjoli of the with 2 lateral primary veins, indicates their resemblance West Kameng District, Arunachal Pradesh (Holotype: to the leaves of only 3 genera, Cinnamomum Schaeffer, Specimen no. CUH/PPL/P/29a). Same locality (Paratypes: Neolitsea (Bentham & J.D.Hooker) Merrill, and Lindera CUH/PPL/P/29b; CUH/PPL/P/2; CUH/PPL/P/9b; CUH/ Thunb., of the family Lauraceae. Two species of Lindera PPL/P/27a-c). show general similarity with the fossils, L. caudata Nees Stratigraphic horizon: Lower part of the Siwalik and L. melastomecea Fern.-Vill., but in both of them the succession (Dafla Formation). leaves are relatively smaller. Moreover, the middle part of Age: Middle to Upper Miocene. the leaves is broadest, whereas in the fossil specimens the Etymology: Adding the prefix ‘palaeo’ to the modern upper half is broader. Leaves of some species of Neolitsea comparable specific epithet bejolghota. (such as N. scorbiculata Gamble) show fairly good Remarks: The most important diagnostic feature of the resemblance to the fossil leaf, but the shape in Neolitsea recovered fossil leaves, i.e. basal acrodromous venation is ovate in contrast to the narrow oblong shape of the

460 KHAN and BERA / Turk J Bot fossil specimen. Furthermore, the leaves in Neolitsea are venation pattern. C. mioinuctum differs from the present relatively smaller. The fossil specimens thus show closer fossils in having an eucamptodromous type of venation as resemblance to the leaves of Cinnamomum. Gamble (1972) compared to the acrodromous venation. The other earlier enumerated 24 species of this genus from India. reported species, such as C. miotavoyanum, C. nepalensis, The fossil leaves have been compared with different C. palaeotamala, Cinnamomum sp., and C. eokachchhensis, modern species of Cinnamomum such as C. pauciflorum mostly differ in possessing an ovate to narrow elliptic Nees, C. burmannii Blume, C. tavoyanum Meisn., C. shape in contrast to the narrow oblong shape in the tamala (Buch.-Ham.) T.Nees & Eberm., C. sulphuratum present fossils. Moreover, in these specimens, the middle Nees, C. obtusifolium Nees, C. caudatum Nees, C. part is broadest, in contrast to the upper broader part in zeylanicum Blume, C. camphora (L.) J.Presl., C. nitidum the present fossil specimens. The present fossil leaves have Blume, C. bejolghota (Buch.-Ham.) Sweet, and C. thus been assigned a new specific name, Cinnamomum macrocarpum Hook. f., and it was found that they have palaeobejolghota Khan & Bera sp. nov. the best resemblance to Cinnamomum bejolghota in size, shape, and venation pattern (Figures 6 and 7). Leaves of 4. Discussion C. tavoyanum, C. tamala, C. sulphuratum, C. obtusifolium, The leaf remains described in the present communication, C. caudatum, C. zeylanicum, and C. camphora attain an along with the earlier fossil records from the Dafla ovate-elliptic shape as compared to the narrow oblong Formation (= lower part of the Siwalik) and Subansiri shape in the present fossil specimens. On the other hand, Formation (= middle part of the Siwalik) of the West leaves of C. pauciflorum, C. burmannii, and C. nitidum Kameng District, are useful in evaluating the palaeoclimate are comparatively smaller in size. Moreover, the lateral of the region. primary veins of these modern leaves lost their identity Most of the earlier fossil records of the Lauraceae towards the apical part. In C. pauciflorum, the lamina is come from the Siwalik sedimentary strata of India (except lanceolate-ovate in shape. In leaves of C. macrocarpum, the Jammu) and Nepal, i.e. the Middle (Pliocene) and Lower middle part is broadest, in contrast to the upper broader (Middle Miocene) Siwalik sediments of Himachal Pradesh part in the present fossil specimens. However, lateral (Mathur, 1978; Mathur et al., 1996); the Lower Siwalik primary veins as well as basal part are comparatively less (Middle Miocene) sediments of the Kathgodam area, acute than those in the fossil specimens. Uttaranchal (Lakhanpal and Guleria, 1978; Prasad, 1994; There are 10 fossil records of Cinnamomum leaves Shashi et al., 2008); the Lower-Middle Siwalik sediments from India and Nepal (Table 1). Pathak (1969) reported (Middle Miocene to Pliocene) of Darjeeling (Pathak, 1969; a leaf of Cinnamomum sp. cf. C. tamala Nees. from Antal and Awasthi, 1993); the Lower Siwalik (Middle to the Middle Siwalik sediments in the Mahanadi River Upper Miocene) sediments of West Kameng District, section, near Darjeeling, West Bengal. C. eokachchhensis Arunachal Pradesh (Srivastava and Mehrotra, 2009); (Lakhanpal and Guleria, 1981) was reported from the the Upper Siwalik (Upper Pliocene-Lower Pleistocene) Eocene of Kachchh, western India, while C. palaeotamala of Papumpare District, Arunachal Pradesh (Khan et al., (Lakhanpal and Awasthi, 1984) was described from the 2011); and the Lower Siwalik (Middle Miocene) sediments Siwalik sediments of Bhikhnathoree, West Champaran of western Nepal (Prasad, 1990; Konomatsu and Awasthi, District of Bihar. C. palaeotamala was also reported from 1996; Prasad and Pandey, 2008). The present record of the Lower Siwalik sediments of Nepal by Konomatsu lauraceous leaves from the Lower (Middle to Upper and Awasthi (1996). C. mioinuctum (Prasad, 1990) was Miocene) and Middle Siwalik (Pliocene) sediments of described from the Lower Siwalik sediments exposed near Arunachal Pradesh in appreciable number and earlier Koilabas, Nepal. Awasthi and Srivastava (1992) and Antal records suggest that it was a common forest element and Awasthi (1993) reported Cinnamomum sp. from the growing in parts of north-western, central, and eastern Warkalli Formation (Miocene) of Kerala and from the Himalayan sectors during the Siwalik sedimentation Lower-Middle Siwalik sediments of Darjeeling, West (Middle Miocene-Lower Pleistocene). Bengal, respectively. Prasad and Pandey (2008) and Shashi On the basis of geographic distribution and climatic et al. (2008) described another leaf of C. nepalensis from preferences of the modern comparable taxa, it appears the lower Siwalik sediments of Surai Khola, western Nepal, that the studied lauraceous taxa are confined to the and Uttaranchal, respectively. A fossil leaf of Cinnamomum evergreen forests of India and neighbouring South-East tavoyanum Meisn. was also reported by Shashi et al. (2008) Asian countries where conditions are more suitable for from the Lower Siwalik sediments of Uttaranchal. their luxuriant growth. Lindera bifaria (Ness) Hook. f., A comparison of the present fossil leaves with all the nearest modern counterpart of one fossil specimen, the above known species showed that earlier described is a small evergreen tree (2–10 m tall) growing in valleys species differ from the present fossils in size, shape, and or on mountain slopes (700–2500 m) of China (Fujian,

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Guangdong, Guangxi, Hainan, Jiangxi, Sichuan, SE There is a well-accepted hypothesis that the land Xizang, Yunnan), Myanmar (Kachin, Mandalay), Bhutan, connection between the Indian plate and the mainland India, Nepal, and Vietnam (Brandis, 1971; Gamble, 1972). masses of South-East Asia was established during the In India, this species occurs in the Himalaya from Kumaon Neogene (Smith and Briden, 1979), causing possible eastwards (1524 m), Manipur, Upper Assam, Mishmi Hills, migration of some tropical plants from South-East Asia and Khasi Hills (914–1219 m). The other comparable to the Indian subcontinent and vice versa (Bande and taxon, Persea glaucescens (Nees) D.G.Long, is a medium- Prakash, 1986). So far, the present fossil taxa have not sized evergreen tree (8–22 m tall) found to grow in China been reported from either the Palaeogene or the Neogene (Yunnan), Bangladesh, Bhutan, India (Western Ghats and of South-East Asia (Bande and Prakash, 1986; Mehrotra et adjoining hill ranges, sub-Himalayan tract), Myanmar, al., 2005), and their present occurrence from the Neogene and Nepal. Persea parviflora Spreng. is a small tree of India suggests a probable migration of these lauraceous distributed in the evergreen forests of India (Khasi Hills, taxa from the Indian landmass to South-East Asian regions Assam, at 1219–1524 m) and the Malayan region (Brandis, after the land connections between these 2 land masses 1971; Hooker, 1999). Cinnamomum bejolghota (Buch.- were established during the Neogene (Figure 8). Ham.) Sweet, the nearest modern counterpart of our fossil It is interesting to note that, at present, Persea specimens, grows in the sparse or dense evergreen forests parviflora is not a common element in the vegetation of on mountain slopes and valleys (600–1800 m) of China the West Kameng District from which the fossil leaves (Guangdong, Hainan, Yunnan), Bangladesh, Bhutan, were recovered (Giri et al., 2008). This species is now India, Laos, Myanmar, Nepal, Thailand, and Vietnam growing in the dense tropical evergreen rain forests of the (Gamble, 1972). Siang and Tirap districts. It is presumed that significant

o o 100 60

o 60

o 50

o 0

o 0 o 10

o 10

Modern distribution of studied lauraceous taxa 100o Fossil locality Arrows indicating the possible migratory path of studied lauraceous taxa in Southeast Asia

Figure 8. Showing modern distribution and possible migratory path of studied lauraceous taxa in South-East Asia.

462 KHAN and BERA / Turk J Bot drying of the climate due to the Himalayan orogeny during to that of the areas of distribution of the living relatives. Miocene to Pliocene times might be a possible reason for The modern analogues of fossil specimens described the disappearance of this species of Lauraceae from the above form a natural association in the evergreen present-day vegetation in the fossil locality and that it forests of India and South-East Asia and suggest that migrated to the moist evergreen forests of the bordering during Siwalik sedimentation forests developed under districts of Arunachal Pradesh and adjoining south-east a tropical, warm, humid climate. This is consistent with Asian regions. the earlier interpretations based on megaplant fossil data It is thought that after the first (HOM-1 during Middle (Mehrotra et al., 1999; Bera et al., 2004; Joshi et al., 2003; Eocene) and second (HOM-2 in Upper Oligocene) Joshi and Mehrotra, 2007; Khan and Bera, 2007, 2010; phases of the Himalayan orogenic movement (HOM), the Bera and Khan, 2009; Srivastava and Mehrotra, 2009; Siwalik sedimentation in Arunachal Pradesh continued Khan et al., 2008, 2009, 2011). However, at present, a through the Miocene into the Lower Pleistocene (Kumar, tropical semievergreen forest cover is found in the area 1997). Epeirogenic uplift of Himalaya (HOM-3) became of investigation (Hazra et al., 1996). This clearly shows quite strong during the Upper Pliocene and Siwalik that there has been a substantial change in the climate sedimentation terminated due to strong compressional of this region since the Mio-Pliocene time. Furthermore, forces of the last phase of the HOM (HOM-4). Himalayan uplift is likely to have been responsible for Thus, gradual changes in climate and physiography this change. Foliar physiognomic characters of the fossil mainly caused by the strong uplift of the Himalaya through leaves such as tip, base, size, margin, and venation pattern Miocene to Lower Pleistocene time brought considerable are also in conformity with our interpretation of climatic alteration and diversification in the floral pattern. Some of conditions in the Arunachal sub-Himalaya during Siwalik the taxa could adapt to the changed climatic conditions sedimentation. and continued to flourish there, while others either suffered extinction in the region or migrated to suitable Acknowledgements areas with tropical littoral and swampy conditions. Thus, it The Department of Science and Technology, New Delhi, is assumed that Persea parviflora might have disappeared is acknowledged for financial assistance. The authors are from West Kameng and adjoining areas of the Arunachal thankful to Sri Bimalendu De, Ex Dy. D.G., and Sri Sambhu sub-Himalaya and later migrated to regions with congenial Chakrabarty, Sr. Geologist, Geological Survey of India, ecoclimatic conditions for its survival. Operation Arunachal, Itanagar, for help and cooperation Based on analysis of the nearest living species, we during the collection of fossil specimens. Thanks are also conclude that the climate of the Siwalik sediments in the due to the authorities of the Central National Herbarium, West Kameng District during the Mio-Pliocene was close Sibpur, Howrah, for permission to consult the Herbarium.

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