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Palaeoecologic significance of some fungi from the miocene of Tanakpur (U.P.) India
Review of Palaeobotany and Palynology, 59 (1989): 127 131
Elsevier Science Publishers B.V., Amsterdam
127
Printed in The Netherlands
PALAEOECOLOGIC SIGNIFICANCE OF SOME FUNGI FROM THE MIOCENE OF TANAKPUR (U.P.)INDIA N.R. PHADTARE Palynology Laboratory, Wadia Institute of Himalayan Geology, Dehra Dun - - 248001 (India)
(Received August 20, 1987; revised and accepted July 14, 1988)
Abstract Phadtare, N.R., 1989. Palaeoecologic significance of some fungi from the Miocene of Tanakpur (U.P.) India. Rev. Palaeobot. Palynol., 59:127 131. Microthyriaceous fructifications assigned to the form genera Callimothallus and Trichothyrites, and a cleistothecium, recovered from fossil leaves, are reported for the first time from calcareous shales of the Lower Siwaliks (M. Miocene) of the Southern Himalayan foothills. Based on the ecologic distribution of their extant analogues, the palaeoecologicsignificance of these fossil fungi is discussed.
Introduction Lower and Middle Siwalik exposures extend all along the s o u th e r n H i m a l a ya n foothills and have yielded a variety of plant fossils (Awasthi, 1982). However, the Upper Siwalik boulder conglomerates are relatively poor in fossil plants (Mathur, 1984). Based on angiosperm plant remains reported so far, L akhanpal (1970) and Awasthi (1982) have inferred the floristic composition and palaeoecologic conditions prevailing during Siwalik deposition. Dispersed fungal spores have also been reported from several Siwalik exposures (Singh and Saxena, 1981; Singh, 1982). Unlike other plant remains, however, fossil fungi have not received due consideration for their utility in palaeoecologic reconstructions. This is caused by their scarcity, as well as poor preservation of the delicate vegetative mycelium and reproductive structures. Like bacteria, fungi are significant decomposers and essential members of every terrestrial plant ecosystem (Odum, 1971). Being nut r i t i ona l l y 0034-6667/89/$03.50
dependent, the total biomass of fungi in any such ecosystem is much less t han the rest of the plant biomass, and thus, the amount of fungi in any fossiliferous sample, if present, is far less than other plant material. During sample processing, because of uniform mixing with other recovered plant material, it gets diluted further. To some extent, lack of mycological expertise may hinder the identification of fragmentary fossil fungal remains (Smoot and Taylor, 1985). Often, fossil fungi preserved along with other plant material are mainly parasitic and symbiotic in habitat (Stubblefield et al., 1984) though saprophytes are not uncommon (Dennis, 1970). Availability of a suitable host is the main factor determining the occurrence of parasitic and symbiotic fungi. On the other hand, the distribution of saprophytes (mainly terrestrial) is predominantly controlled by other factors like humidity, temperature and humus. Evidently therefore, the understanding of the palaeoecology will be enhanced if analysis of the contemporary flora is coupled
g') 1989 Elsevier Science Publishers B.V.
128 with detailed study of associated fungal remains. In this communication, the epiphytic remains of microthyriaceous reproductive structures are reported for the first time from the Lower Siwaliks of Tanakpur area, and their role in depicting the ecology and nature of vegetation existing at the time of deposition is described.
Material and m e t h o d s Calcareous shales of the Lower Siwaliks exposed along the Kali river section near Thuli Gad, about 18 km NE of Tanakpur, are rich in angiosperm leaf compressions. During our recent field work, a variety of leaf compressions has been collected. The samples were photographed and studied for their gross and detailed morphology. With conventional laboratory techniques, individual leaf samples were macerated for cuticular recovery. Almost every cuticular fragment yielded a good amount of epiphyllous fungi. Each recovered fungal reproductive structure has been described systematically in the modified natural classification system of Dilcher (1965).
S y s t e m a t i c description Division: FUNGI Class: ASCOMYCETES Family: MICROTHYRIACEAE
Genus:
CaIIimothallus
Callimothallus (Figs.1 3)
Dilcher, 1965
pertusus
Dilcher,
1965
Description: Ascomata discoid, circular, rediate, nonostiolate, variable in size; margin smooth, slightly thinning; central cells of stroma distinctly thickened, polygonal; other part of stroma made up of radially elongated, thick walled, rectangular and porate cells, mycelium absent. Remarks: This genus has been reported for the first time from the Siwalik exposures. The form genus Callimothallus is one of the well established and widely reported genera of fossil microthyriaceous fungi. In Indian Tertiary
deposits, it has been reported e.g. from the Tura Formation of Assam (Kar et al., 1970), the Edvi lignite (Rao and Ramanujam, 1976) of South India and Ratnagiri lignite (Phadtare, 1982) of Maharashtra. All these reports indicate that the genus Callimothallus has a wide stratigraphic distribution (Paleocene M. Miocene). Distribution: Profusely colonising on adaxial surface of fossil leaves which are closely resembling the genus Diospyros (Ebenaceae). Clusters of this reproductive structure are found to be directly or closely associated with costal areas of the leaf epidermis (Fig.l). This clearly denotes its nutritional dependability and hence the parasitic or symbiotic habitat.
Genus:
Triehothyrites
Rosendahl, 1943
Trichothyrites siwalikus sp. nov. (Figs.4, 5) Description: Ascomata of variable sizes, slightly to distinctly excentric, profusely and deeply lobed along perifery, ostiolate, radiate; individual cell distally porate, rectangular, elongated along the radius, thinning towards the periphery, mycelium lacking. Remarks: Different species of the genus Trichothyrites have been reported from Indian Tertiary exposures. T. denticulatus reported from Warkalli (Ramanujam and Rao, 1971) has denticulate projections inside the ostiole cavity. Kar and Saxena (1974) and Phadtare (1982) have reported T. amorphus from the Matanomadh Formation and Ratnagiri lignite respectively with an amorphous nature. The morphotype described above can be differentiated from other species of this genus by its distinctly lobed and excentric nature. This new taxon is named after the Siwaliks from where it has been reported for the first time. Holotype: Fig.5 Slide: LS/Tnkp/-20 Locality: Lower Siwalik of Tanakpur (U.P.) India. Age: M. Miocene. Distribution: It is confined to abaxial surface of fossil leaves comparable with Diospyros of Ebenaceae. Its random distribution on leaf
129
°
,'~'i0.m
:
~
3
5o,~,,,
6
Fig.1. Adaxial leaf epidermis showing clusters of Callimothallus reproductive structures closely associated with costa] cells. Fig.2. Young reproductive structure of Callimothallus. Fig.3. Callimothallus pertusus. Fig.4. Abaxial epidermis of the same leaf showing random distribution of Trichothyrites fructifications. Fig.5. Trichothyrites siwalikus sp. nov.; ho]otype. Fig.6. C]eistothecial type of ascocarp.
130
epidermal tissue is suggestive of symbiotic nature of association.
Fungal fructification "A" (Fig.6)
Description: Fructing structure globular, about 100-120 pm in diameter, thick walled, prominently stalked, stalk about 120 150 pm long, multicellular, multiseriate, fibrous; vegetative mycelium absent. Remarks: General morphology of t h i s fruiting structure clearly hints toward a cleistothecial type of ascocarp. Ascospores however, are not found. Affinity: Ascomycetes.
Ecologic considerations Extant members of the family Microthyriaceae, like other epiphyllous fungi, are relatively indifferent in host selection. It is one of the most dominant fungal families presently thriving in luxuriant vegetations of Western Ghats and Malaysian islands (Phadtare, 1982). Wet tropical climate sustaining evergreen, semi-deciduous-deciduous vegetations, is an ideal habitat for these fungi. They commonly grow in association with other sooty moulds like those of the Meliolinae (Dilcher, 1965). Today in closed forests of tropics and subtropics the epiphyllous fungi have a distinct pattern of vertical distribution. They generally grow only on the lower surface of leaves in the basal part of the upper canopy and the upper part of the middle canopy. However, they profusely colonize on both surfaces of leaves in the central and lower parts of the middle canopy. Such a distribution pattern, as is the case about the higher plants, may be dependent on atmospheric factors such as light and rain fall. Leaf surfaces receiving direct sun light (mainly those from the uppermost part of the upper canopy) for example, may become dried immediately after rain, which thus prevents the growth of epiphyllous fungal germlings. Heavy and regular precipitation may prevent such colonization on adaxial leaf surfaces of the upper canopy. Exposure of upper canopy
leaves to open aeration, to some extent, may also be a factor in such failure of fungal colonization.
Vegetation pattern The abundance of microthyriaceous fungi in association with Miocene fossil leaves suggests that the coexisting vegetation was considerably thick and of a close type so as to sustain high humidity with almost uniform and warm temperature and to allow little penetration of light as well as wind. The presence of varieties of mesophyllous leaves also suggests that the vegetation was composed of many plant taxa representing a heterogeneous community. Today in this type of vegetation, the herbaceous flora (lower and ground canopy members) is practically absent or highly depleted. This could be one of the obvious reasons, like non-preservation due to oxidizing depositional environment, for the virtual absence of herbaceous families in this fossil flora. Relatively little decomposition, virtual lack of distortion and general intactness of recovered fossil leaves clearly indicate that they have not travelled any appreciable distance before deposition. Sedimentological aspects of the fossiliferous beds bearing these leaf remains indicate a fining upward sequence, the characteristic feature of a low energy flood plain or protected lacustrine depositional environment. All these evidences collectively show that possibly the vegetation was thriving close to the depositional site. Amongst the fossil leaf compressions so far collected from this locality, well developed matting of microthyriaceous fructifications were found to be closely associated with both surfaces of leaves resembling Diospyros of Ebenaceae. It certainly indicates that the host plant (i.e. Diospyros) was a member of the middle canopy. Diospyros, a prominent genus of this family (Lawrence, 1951) is one of the important members of present day tropical to subtropical forests. Leaf impressions resembling Diospyros embryopteris have already been reported from the Siwaliks exposed near
131
Hardwar (Verma, 1968). Fossil woods affiliated to this genus have also been reported from the Lower Siwaliks (Prakash, 1981). Amongst the angiosperm families reported from the Lower Siwaliks (Awasthi, 1982), the Annonaceae, Ebenaceae, Leguminosae (some members), Rhamnaceae, Rosaceae and Smilacaceae are the prominent members of the middle canopy. Families like Dipterocarpaceae, Sterculiaceae, Combretaceae, Anacardiaceae and Meliaceae are the occupants of the upper canopy. Lower canopy members like herbaceous families are practically absent in the Lower Siwaliks of Tanakpur. All the woody families reported from the Lower Siwaliks are deciduous to semi-deciduous in nature.
Summary and conclusions For the first time, microthyriaceous epiphytic fungi assigned to the form genera Callimothallus and Trichothyrites, have been reported from the Lower Siwaliks of Tanakpur. The present findings, together with existing literature on the palaeoflora of the Lower Siwaliks, lead to the following inferences. (1) Excellent preservation and richness of the fossil leaves indicate that the source vegetation contributing to the Lower Siwaliks of Tanakpur, existed not far from the site of its deposition. (2) Heavy rain fall and high humidity was prevailing at the time of deposition. (3) A thick and close canopy type of deciduous to semi-deciduous vegetation was thriving near the depositional source. (4) The richness and composition of the palaeovegetation along with sedimentary features indicate that considerably low slope leading immediately to plains rich in soil and humus, must have existed near the depositional site. Low land topography is of prime importance to sustain thick and closed deciduous forest.
Acknowledgements Author is thankful to Dr. S.C.D. Sah, Director Wadia Institute of Himalayan Geology for
permission to carry out this research, his constant encouragement and critically revising the manuscript. Thanks are also due to Dr. B.N. Tiwari for his help in fieldwork.
References Awasthi, N., 1982. Tertiary plant megafossils from the Himalaya - - A review. Palaeobotanist, 30: 254-267. Dennis, R.L., 1970. A Middle Pennsylvanian basidiomycet mycelium with clamp connection. Mycologia, 62:578 584. Dilcher, D.L., 1965. Epiphyllous fungi from Eocene deposits in Western Tennessee, U.S.A. Palaeontographica, l16B: 1 54. Kar, R.K. and Saxena, R.K., 1974. Algal and fungal microfossils from M a t a n o m a d h Formation (Palaeocene), Kutch, India. Palaeobotanist, 23: 1-15. Kar, R.K., Singh, R.Y. and Sah, S.C.D., 1970. On some algal and fungal remains from Tura Formation of Garo Hills, Assam. Palaeobotanist, 19: 146-154. Lakhanpal, R.N., 1970. Tertiary floras of India and their bearing on the historical geology of the region. Taxon, 19:675 694. Lawrence, G.H.M., 1951. Taxonomy of vascular plants. Macmillan, N.Y., 823 pp. Mathur, Y.K., 1984. Cenozoic palynofossils, vegetation, ecology and climate of the n o r t h and northwestern subhimalayan region. In: R.O. Whyte (Editor), The Evolution of the East Asian Environment. Vol. II. Univ. Hong Kong, pp.504 551. Odum, E.P., 1971. Fundamentals of Ecology. Saunders, London. 574 pp. Phadtare, N.R., 1982. Floristic studies on the lignitic beds of Ratnagiri District, M a h a r a s h t r a . Thesis, Univ. Bombay, 275pp. Prakash, U., 1981. Further occurrence of fossil woods from the Lower Siwalik beds of U t t a r Pradesh, India. Palaeobotanist, 28-29:374 383. Ramanujam, C.G.K. and Rao, K.P., 1971. On some microthyriaceous fungi from Tertiary lignite of south India. Palaeobotanist, 20: 203-209. Rao, K.P. and Ramanujam, C.G.K., 1976. A further record of microthyriaceous fungi from the Neogene deposits in South India. Geophytology, 6:98 104. Rosendahl, C.O., 1943. Some fossil fungi from Minnesota. Bull. Torrey Bot. Club, 70:126 138. Singh, H.P., 1982. Tertiary palynology of the Himalaya - A review. Palaeobotanist, 30: 268-278. Singh, H.P. and Saxena, R.K., 1981. Palynology of the Upper Siwalik sediments in U n a district, Himachal Pradesh. Geophytology, 173-181. Smoot, E.L. and Taylor, T.N., 1985. Palaeobotany: Recent developments and future research directions. Palaeogeogr. Palaeoclimatol. Palaeoecol., 50: 149-162. Stubblefield, S.P., Taylor, T.N. and others, 1984. Studies on Paleozoic fungi III. Fungal parasitism in Pennsylvanian gymnosperms. Am. J. Bot., 71:1275 1282. Verma, C.P., 1968. On the collection of leaf impressions from Hardwar, U t t a r Pradesh. J. Palaeontol. Soc. India, 5-9:93 98.
Elsevier Science Publishers B.V., Amsterdam
127
Printed in The Netherlands
PALAEOECOLOGIC SIGNIFICANCE OF SOME FUNGI FROM THE MIOCENE OF TANAKPUR (U.P.)INDIA N.R. PHADTARE Palynology Laboratory, Wadia Institute of Himalayan Geology, Dehra Dun - - 248001 (India)
(Received August 20, 1987; revised and accepted July 14, 1988)
Abstract Phadtare, N.R., 1989. Palaeoecologic significance of some fungi from the Miocene of Tanakpur (U.P.) India. Rev. Palaeobot. Palynol., 59:127 131. Microthyriaceous fructifications assigned to the form genera Callimothallus and Trichothyrites, and a cleistothecium, recovered from fossil leaves, are reported for the first time from calcareous shales of the Lower Siwaliks (M. Miocene) of the Southern Himalayan foothills. Based on the ecologic distribution of their extant analogues, the palaeoecologicsignificance of these fossil fungi is discussed.
Introduction Lower and Middle Siwalik exposures extend all along the s o u th e r n H i m a l a ya n foothills and have yielded a variety of plant fossils (Awasthi, 1982). However, the Upper Siwalik boulder conglomerates are relatively poor in fossil plants (Mathur, 1984). Based on angiosperm plant remains reported so far, L akhanpal (1970) and Awasthi (1982) have inferred the floristic composition and palaeoecologic conditions prevailing during Siwalik deposition. Dispersed fungal spores have also been reported from several Siwalik exposures (Singh and Saxena, 1981; Singh, 1982). Unlike other plant remains, however, fossil fungi have not received due consideration for their utility in palaeoecologic reconstructions. This is caused by their scarcity, as well as poor preservation of the delicate vegetative mycelium and reproductive structures. Like bacteria, fungi are significant decomposers and essential members of every terrestrial plant ecosystem (Odum, 1971). Being nut r i t i ona l l y 0034-6667/89/$03.50
dependent, the total biomass of fungi in any such ecosystem is much less t han the rest of the plant biomass, and thus, the amount of fungi in any fossiliferous sample, if present, is far less than other plant material. During sample processing, because of uniform mixing with other recovered plant material, it gets diluted further. To some extent, lack of mycological expertise may hinder the identification of fragmentary fossil fungal remains (Smoot and Taylor, 1985). Often, fossil fungi preserved along with other plant material are mainly parasitic and symbiotic in habitat (Stubblefield et al., 1984) though saprophytes are not uncommon (Dennis, 1970). Availability of a suitable host is the main factor determining the occurrence of parasitic and symbiotic fungi. On the other hand, the distribution of saprophytes (mainly terrestrial) is predominantly controlled by other factors like humidity, temperature and humus. Evidently therefore, the understanding of the palaeoecology will be enhanced if analysis of the contemporary flora is coupled
g') 1989 Elsevier Science Publishers B.V.
128 with detailed study of associated fungal remains. In this communication, the epiphytic remains of microthyriaceous reproductive structures are reported for the first time from the Lower Siwaliks of Tanakpur area, and their role in depicting the ecology and nature of vegetation existing at the time of deposition is described.
Material and m e t h o d s Calcareous shales of the Lower Siwaliks exposed along the Kali river section near Thuli Gad, about 18 km NE of Tanakpur, are rich in angiosperm leaf compressions. During our recent field work, a variety of leaf compressions has been collected. The samples were photographed and studied for their gross and detailed morphology. With conventional laboratory techniques, individual leaf samples were macerated for cuticular recovery. Almost every cuticular fragment yielded a good amount of epiphyllous fungi. Each recovered fungal reproductive structure has been described systematically in the modified natural classification system of Dilcher (1965).
S y s t e m a t i c description Division: FUNGI Class: ASCOMYCETES Family: MICROTHYRIACEAE
Genus:
CaIIimothallus
Callimothallus (Figs.1 3)
Dilcher, 1965
pertusus
Dilcher,
1965
Description: Ascomata discoid, circular, rediate, nonostiolate, variable in size; margin smooth, slightly thinning; central cells of stroma distinctly thickened, polygonal; other part of stroma made up of radially elongated, thick walled, rectangular and porate cells, mycelium absent. Remarks: This genus has been reported for the first time from the Siwalik exposures. The form genus Callimothallus is one of the well established and widely reported genera of fossil microthyriaceous fungi. In Indian Tertiary
deposits, it has been reported e.g. from the Tura Formation of Assam (Kar et al., 1970), the Edvi lignite (Rao and Ramanujam, 1976) of South India and Ratnagiri lignite (Phadtare, 1982) of Maharashtra. All these reports indicate that the genus Callimothallus has a wide stratigraphic distribution (Paleocene M. Miocene). Distribution: Profusely colonising on adaxial surface of fossil leaves which are closely resembling the genus Diospyros (Ebenaceae). Clusters of this reproductive structure are found to be directly or closely associated with costal areas of the leaf epidermis (Fig.l). This clearly denotes its nutritional dependability and hence the parasitic or symbiotic habitat.
Genus:
Triehothyrites
Rosendahl, 1943
Trichothyrites siwalikus sp. nov. (Figs.4, 5) Description: Ascomata of variable sizes, slightly to distinctly excentric, profusely and deeply lobed along perifery, ostiolate, radiate; individual cell distally porate, rectangular, elongated along the radius, thinning towards the periphery, mycelium lacking. Remarks: Different species of the genus Trichothyrites have been reported from Indian Tertiary exposures. T. denticulatus reported from Warkalli (Ramanujam and Rao, 1971) has denticulate projections inside the ostiole cavity. Kar and Saxena (1974) and Phadtare (1982) have reported T. amorphus from the Matanomadh Formation and Ratnagiri lignite respectively with an amorphous nature. The morphotype described above can be differentiated from other species of this genus by its distinctly lobed and excentric nature. This new taxon is named after the Siwaliks from where it has been reported for the first time. Holotype: Fig.5 Slide: LS/Tnkp/-20 Locality: Lower Siwalik of Tanakpur (U.P.) India. Age: M. Miocene. Distribution: It is confined to abaxial surface of fossil leaves comparable with Diospyros of Ebenaceae. Its random distribution on leaf
129
°
,'~'i0.m
:
~
3
5o,~,,,
6
Fig.1. Adaxial leaf epidermis showing clusters of Callimothallus reproductive structures closely associated with costa] cells. Fig.2. Young reproductive structure of Callimothallus. Fig.3. Callimothallus pertusus. Fig.4. Abaxial epidermis of the same leaf showing random distribution of Trichothyrites fructifications. Fig.5. Trichothyrites siwalikus sp. nov.; ho]otype. Fig.6. C]eistothecial type of ascocarp.
130
epidermal tissue is suggestive of symbiotic nature of association.
Fungal fructification "A" (Fig.6)
Description: Fructing structure globular, about 100-120 pm in diameter, thick walled, prominently stalked, stalk about 120 150 pm long, multicellular, multiseriate, fibrous; vegetative mycelium absent. Remarks: General morphology of t h i s fruiting structure clearly hints toward a cleistothecial type of ascocarp. Ascospores however, are not found. Affinity: Ascomycetes.
Ecologic considerations Extant members of the family Microthyriaceae, like other epiphyllous fungi, are relatively indifferent in host selection. It is one of the most dominant fungal families presently thriving in luxuriant vegetations of Western Ghats and Malaysian islands (Phadtare, 1982). Wet tropical climate sustaining evergreen, semi-deciduous-deciduous vegetations, is an ideal habitat for these fungi. They commonly grow in association with other sooty moulds like those of the Meliolinae (Dilcher, 1965). Today in closed forests of tropics and subtropics the epiphyllous fungi have a distinct pattern of vertical distribution. They generally grow only on the lower surface of leaves in the basal part of the upper canopy and the upper part of the middle canopy. However, they profusely colonize on both surfaces of leaves in the central and lower parts of the middle canopy. Such a distribution pattern, as is the case about the higher plants, may be dependent on atmospheric factors such as light and rain fall. Leaf surfaces receiving direct sun light (mainly those from the uppermost part of the upper canopy) for example, may become dried immediately after rain, which thus prevents the growth of epiphyllous fungal germlings. Heavy and regular precipitation may prevent such colonization on adaxial leaf surfaces of the upper canopy. Exposure of upper canopy
leaves to open aeration, to some extent, may also be a factor in such failure of fungal colonization.
Vegetation pattern The abundance of microthyriaceous fungi in association with Miocene fossil leaves suggests that the coexisting vegetation was considerably thick and of a close type so as to sustain high humidity with almost uniform and warm temperature and to allow little penetration of light as well as wind. The presence of varieties of mesophyllous leaves also suggests that the vegetation was composed of many plant taxa representing a heterogeneous community. Today in this type of vegetation, the herbaceous flora (lower and ground canopy members) is practically absent or highly depleted. This could be one of the obvious reasons, like non-preservation due to oxidizing depositional environment, for the virtual absence of herbaceous families in this fossil flora. Relatively little decomposition, virtual lack of distortion and general intactness of recovered fossil leaves clearly indicate that they have not travelled any appreciable distance before deposition. Sedimentological aspects of the fossiliferous beds bearing these leaf remains indicate a fining upward sequence, the characteristic feature of a low energy flood plain or protected lacustrine depositional environment. All these evidences collectively show that possibly the vegetation was thriving close to the depositional site. Amongst the fossil leaf compressions so far collected from this locality, well developed matting of microthyriaceous fructifications were found to be closely associated with both surfaces of leaves resembling Diospyros of Ebenaceae. It certainly indicates that the host plant (i.e. Diospyros) was a member of the middle canopy. Diospyros, a prominent genus of this family (Lawrence, 1951) is one of the important members of present day tropical to subtropical forests. Leaf impressions resembling Diospyros embryopteris have already been reported from the Siwaliks exposed near
131
Hardwar (Verma, 1968). Fossil woods affiliated to this genus have also been reported from the Lower Siwaliks (Prakash, 1981). Amongst the angiosperm families reported from the Lower Siwaliks (Awasthi, 1982), the Annonaceae, Ebenaceae, Leguminosae (some members), Rhamnaceae, Rosaceae and Smilacaceae are the prominent members of the middle canopy. Families like Dipterocarpaceae, Sterculiaceae, Combretaceae, Anacardiaceae and Meliaceae are the occupants of the upper canopy. Lower canopy members like herbaceous families are practically absent in the Lower Siwaliks of Tanakpur. All the woody families reported from the Lower Siwaliks are deciduous to semi-deciduous in nature.
Summary and conclusions For the first time, microthyriaceous epiphytic fungi assigned to the form genera Callimothallus and Trichothyrites, have been reported from the Lower Siwaliks of Tanakpur. The present findings, together with existing literature on the palaeoflora of the Lower Siwaliks, lead to the following inferences. (1) Excellent preservation and richness of the fossil leaves indicate that the source vegetation contributing to the Lower Siwaliks of Tanakpur, existed not far from the site of its deposition. (2) Heavy rain fall and high humidity was prevailing at the time of deposition. (3) A thick and close canopy type of deciduous to semi-deciduous vegetation was thriving near the depositional source. (4) The richness and composition of the palaeovegetation along with sedimentary features indicate that considerably low slope leading immediately to plains rich in soil and humus, must have existed near the depositional site. Low land topography is of prime importance to sustain thick and closed deciduous forest.
Acknowledgements Author is thankful to Dr. S.C.D. Sah, Director Wadia Institute of Himalayan Geology for
permission to carry out this research, his constant encouragement and critically revising the manuscript. Thanks are also due to Dr. B.N. Tiwari for his help in fieldwork.
References Awasthi, N., 1982. Tertiary plant megafossils from the Himalaya - - A review. Palaeobotanist, 30: 254-267. Dennis, R.L., 1970. A Middle Pennsylvanian basidiomycet mycelium with clamp connection. Mycologia, 62:578 584. Dilcher, D.L., 1965. Epiphyllous fungi from Eocene deposits in Western Tennessee, U.S.A. Palaeontographica, l16B: 1 54. Kar, R.K. and Saxena, R.K., 1974. Algal and fungal microfossils from M a t a n o m a d h Formation (Palaeocene), Kutch, India. Palaeobotanist, 23: 1-15. Kar, R.K., Singh, R.Y. and Sah, S.C.D., 1970. On some algal and fungal remains from Tura Formation of Garo Hills, Assam. Palaeobotanist, 19: 146-154. Lakhanpal, R.N., 1970. Tertiary floras of India and their bearing on the historical geology of the region. Taxon, 19:675 694. Lawrence, G.H.M., 1951. Taxonomy of vascular plants. Macmillan, N.Y., 823 pp. Mathur, Y.K., 1984. Cenozoic palynofossils, vegetation, ecology and climate of the n o r t h and northwestern subhimalayan region. In: R.O. Whyte (Editor), The Evolution of the East Asian Environment. Vol. II. Univ. Hong Kong, pp.504 551. Odum, E.P., 1971. Fundamentals of Ecology. Saunders, London. 574 pp. Phadtare, N.R., 1982. Floristic studies on the lignitic beds of Ratnagiri District, M a h a r a s h t r a . Thesis, Univ. Bombay, 275pp. Prakash, U., 1981. Further occurrence of fossil woods from the Lower Siwalik beds of U t t a r Pradesh, India. Palaeobotanist, 28-29:374 383. Ramanujam, C.G.K. and Rao, K.P., 1971. On some microthyriaceous fungi from Tertiary lignite of south India. Palaeobotanist, 20: 203-209. Rao, K.P. and Ramanujam, C.G.K., 1976. A further record of microthyriaceous fungi from the Neogene deposits in South India. Geophytology, 6:98 104. Rosendahl, C.O., 1943. Some fossil fungi from Minnesota. Bull. Torrey Bot. Club, 70:126 138. Singh, H.P., 1982. Tertiary palynology of the Himalaya - A review. Palaeobotanist, 30: 268-278. Singh, H.P. and Saxena, R.K., 1981. Palynology of the Upper Siwalik sediments in U n a district, Himachal Pradesh. Geophytology, 173-181. Smoot, E.L. and Taylor, T.N., 1985. Palaeobotany: Recent developments and future research directions. Palaeogeogr. Palaeoclimatol. Palaeoecol., 50: 149-162. Stubblefield, S.P., Taylor, T.N. and others, 1984. Studies on Paleozoic fungi III. Fungal parasitism in Pennsylvanian gymnosperms. Am. J. Bot., 71:1275 1282. Verma, C.P., 1968. On the collection of leaf impressions from Hardwar, U t t a r Pradesh. J. Palaeontol. Soc. India, 5-9:93 98.