eastern side of Lauresia during the Upper Albian. Key words ... from the Upper Albian of Hokkaido, Japan. .... (Canada) and their paleoecological significance.
J. Plant Res. 108 : 11-15, 1995
Journal of Plant Research O by The Botanical Society of Japan 1995
Ephedroid Fossil Pollen from the Lower Cretaceous (Upper Albian) of Hokkaido, Japan Masamichi Takahashi 1, Kazuhiro Takai' and Ken'ichi Saiki 2 i Department of Biology, Faculty of Education, Kagawa University, Takamatsu, 760 Japan 2 Department of Plant Science, Natural History Museum and Institute, Chiba, Aoba-cho, Cyuo-ku, Chiba, 260 Japan
This paper presents eight ephedroid palynomorphs from the Lower Cretaceous (Upper Albian) of Hokkaido, Japan. The ephedroid palynomorphs are ellipsoid and polyplicate pollen grains that show a wide range of variation in pollen size, shape, and plication. These ephedroid palynomorphs suggest a wide range of diversity in Gnetales at mid- or high-paleolatitude in the eastern side of Lauresia during the Upper Albian. Key words : Albian - - Cretaceous-- Ephedroid - Fossil - - Pollen
Recent phylogenetic hypotheses place Gnetales as the extant seed plants most closely related to angiopserms (Crane 1985, Doyle and Donoghue 1986a, 1986b). The Gnetales consist of three living genera, Ephedra, Welwitschia and Gnetum. Pollen grains of Ephedra and Welwitschia are elliptic and polyplicate, while pollen grains of Gnetum are inaperturate and spinutose (Wodehouse 1935, Erdtman 1957, 1965, Hesse 1980, 1984, Kedves 1987). Stover (1964) described Cretaceous ephedroid pollen from West Africa. Trevisan (1980) showed exine structure of Ephedripites from the Lower Cretaceous of Italy with transmission electron microscopy (TEM). Osborn et al. (1993) reviewed previous megafossil and palynological records of Gnetales, and documented the ultrastructure of fossil ephedroid pollen from the Lower Cretaceous of Brazil. The present study shows eight polyplicate pollen grains from the Upper Albian of Hokkaido, Japan. This is the first micromorphological study on Lower Cretaceous palynomorphs from an eastern Laurasian locality. Materials and Methods
The materials were collected from the outcrop (no. 2031 : Matsumoto 1965) along the Ponbetsu River, about northeast from Sapporo, Japan. The sediments at this locality are dated as the lowest Upper Albian (Kanie et al. 1993). Palynomorphs were recovered from calcium carbonate nodules obtained from the locality. Preparation was followed standard techniques (Doher 1980). Dehydrated
pollen grains were transferred into benzene and pipetted directly from residues onto polished alminium stubs, sputter coated with platinum/palladium, and then examined in a Hitachi S-800 field emission scanning electron microscope (FE-SEM) at an accelerating voltage of 8 kV. Results
Pollen grains are elliptic and polyplicate with a wide range of variation in pollen size and plicae. The smaller type of pollen grains is 30-33/zm in length and 16-18/zm in width (Figs. l-4). These grains have unbranched and straight plicae that extend for the majority of the length of the grain and almost reach the ends of the grains. The plicae of the first three pollen grains are regularly arranged (Figs. 1-3), although one pollen grain has an aperture (Fig. 4). The larger type of pollen grains is 35-55/zm in length and 13-20/zm in width (Figs. 5-8). These grains have unbranched and somewhat spiral or longitudinal plicae (Figs. 5-8). One of the spiral plicate pollen grains has plicae that extend for the majority of the grain length and almost reach the ends of the grain (Fig. 5). One of the straight plicate pollen grains is characterized ca. thirty narrow striate plicae (Fig. 6), while the other one has eight plicae (Fig. 7). A further pollen grain is not synmetrical and has twisted spiral plicae at one end, although it is uncertain whether this is a feature caused by fossilization process (Fig. 8). Discussion
Crane and Lidgard (1989) compiled 1,125 Cretaceous pollen and spore samples, and showed a striking increase in gnetalean diversity concurrent with the initial angiopserm diversification at low paleolatitudes from Neocomian to Albian periods. The polyplicate palynomorphs from Hokkaido are found almost near the distribution limit of ephedroid pollen grains during Albian period. These ephedroid palynomorphs suggest some of diversity of Gnetales even at mid- or high-paleolatitude in the eastern side of Lauresia in the Upper Albian. Steeves and Barghoorn (1959) described pollen grains of living Ephedra. They distinguished pollen grains of
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Figs. l-4. Smaller type of ephedroid pollen. Bar=lO,um. 1. Polyplicate pollen with wide plicae oriented longitudinally. 2. Polyplicate pollen with narrow plicae oriented longitudinally. 3. Polyplicate pollen with plicae interconnected at the ends. 4. Polyplicate pollen with an aperture.
Cretaceous Ephedroid Pollen
Figs. 5-8. Larger type of ephedroid pollen. Bar=lO,um. 5. Polyplicate pollen with twisted plicae. 6. Polyplicate pollen with many plicae oriented longitudinally. 7. Polyplicate pollen with plicae oriented longitudinally. 8. Polyplicate pollen with twisted plicae.
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living Ephedra into four pollen types (A-D) based on variation in pticae. Pollen grains of some living Ephedra are characterized by undulating plicae (Types A and B). Pollen grains of the other living Ephedra species have straight plicae (Types C and D). The smaller type of ephedroid fossil pollen grains (Figs. 1-3) are similar to the types C and D, in sharing straight plicae. Osborn et al. (1993) investigated ephedroid palynomorphs from the Lower Cretaceous sediments of Brazil with SEM and TEM. They suggested that the palynomophs are most similar to Ephedripites based on their fine structral features, showing a granular infratectum in exine structure (Osborn et al. 1993). These pollen grains average 41/zm in length and 13 ~m in width, are polyplicate patynomorphs with 5-11 plicae. The three smaller pollen grains from Hokkaido resemble Ephedripites in pollen type and plicate orientation. Pollen of Welwitschia mirabilis is plicate and monocolpate (Wodehouse 1935, Zavada and Gabarayeva 1991). Pollen of Welwitschia are very similar to those of Ephedra but are monocolpate rather than inaperturate (Srivastava 1968). One of the present palynomorphs is a monocolpate pollen grain with plicate exine (Fig. 4). The fossil pollen is similar to the pollen of Welwitschia in overall form and the plicate exine ornamentation. Polyplicate palynomoprhs with twisted loops of plicae, as shown in Figs. 5 and 8, have been reproted frequently from Cretaceous sediments (Stover 1964, Srivastava 1968, Philips and Felix 1971, Miki 1972). Pocock and Vasanthy (1988) recently emended palynomorphs Equisetosporites chinleana that is different in surface morphology and exine structure from Ephedripites. In Equisetosporites, exine ribs are psilate and more spiral in their orientation. The fine structure of E. chineleana pollen was also initially realized to be "non-gnetalean", principally because of its columellar infratectum (Zavada 1984): Zavada (1990) has subsequently suggested that these grains are definitively more angiospermous than gymnospermous. The polyplicate palynomorphs with spiral plicae (Figs. 5 and 8) are associated with Equisetosporites. Further investigations are needed to elucidate the exine structure of this and other ephedroid grains with transmission electron microscopy. This study was partly for Scientific Research Science and Culture to Fujiwara Natural History
supported by a Grant-in-Aid (A) from the Ministry of Education, H. Tobe (No. 05304009), and by Foundation to K. Saiki (No. 40).
References Crane, P.R. 1985. Phylogenetic analysis of seed plants and the origin of angiosperms. Ann. Missouri Bot. Gard. 72 : 716-793. Crane, P.R. and Lidgard, S. 1989. Angiosperm diversification and paleolatitudinal gradients in Cretaceous floristic diversity. Science 246: 675-678. Doher, L.I. 1980. Palynomorph preparation procedures
currently used in the paleontology and stratigraphy laboratories, U.S. Geological Survey. U.S. Geol. Surv. Circ. 830, 29 pp. Doyle, J.A. and Donoghue, M.J. 1986a. Seed plant phylogeny and the origin of angiopserms : an experimental cladistic approach. Bot. Rev. 52: 321-431. Doyle, J.A. and Donoghue, M.J. 1986b. Relationships of angiopserms and Gnetales: A numerical cladistic analysis. In R.A. Spicer and B.A. Thomas, eds., Systematic and Taxonomic Approaches in Palaeobotany, Claredon, Oxford, pp. 177-198. Erdtman, G. 1957. Pollen and Spore Morphology/Plant Taxonomy (An Introduction to Palynology II). AImqvist and Wiksell, Stockholm. Erdtman, G. 1965. Pollen and Spore Morphology/Plant Taxonomy (An Introduction to Palynology III). AImqvist and Wiksell, Stockholm. Hesse, M. 1980. Pollenkitt is lacking in Gnetum gnemon (Gnetaceae). PI. Syst. Evol. 136: 41-46. Hesse, M. 1984. Pollenkitt is lacking in Gnetatae : Ephedra and Welwitschia : further proof for its restriction to the angiopserms. PI. Syst. Evol. 144 : 9-16.
Kanie, Y., Yoshikawa, Y., Sakai, T. and Takahashi, T. 1993. The Cretaceous chemosynthetic cold waterdependent molluscan community discovered from Mikasa City, central Hokkaido. Sci. Rep. Yokohama City Mus. 41 : 31-36. (in Japanese). Kedves, M. 1987. LM and EM studies on pollen grains of recent Welwitschia mirabilis Hook and Ephedra species. Acta Bot. Hung. 33 : 81-103. Matsumoto, T. 1965. A monograph of the Collignoniceratidae from Hokkaido, Part I, Studis of the Cretaceous ammonites from Hokkaido and Saghalien XIV. Mem. Fac. Sci. Kyushu Univ. Ser D. 16 : 1-80. Miki, A. 1972. Palynological study of the Kuji Group in northeastern Honshu, Japan. J. Fac. Sci. Hokkaido Univ. Ser. 4, 15 : 513-604. Osborn, J.M, Taylor, T.N. and de Lima, M.R. 1993. The ultrastructure of fossil ephedroid pollen with gnetalean affinites from the Lower Cretaceous of Brazil. Rev. Palaeobot. Palynol. 77: 171-184. Phillips, P.P. and Felix, C.J. 1971. A study of Lower and Middle Cretaceous spores and pollen from the southeastern United States. I1. Pollen. Pollen Spores 13: 447-473. Pocock, S.A.J. and Vasanthy, G. 1988. Cornetipollis reticulata, a new pollen with angiospermid features from Upper Triassic (Carnian) sediments of Arizona (U.S.A.), with notes on Equisetosporites. Rev. Palaeobot. Palynol. 55: 337-356. Srivastava, S.K. 1968. Ephedralean pollen from the Upper Cretaceous Edmonton Formation of Alberta (Canada) and their paleoecological significance. Can. J. Earth Sci. 5: 211-221. Steeves, M.W. and Barghoorm, E.S. 1959. The pollen of Ephedra. J. Arnold Arbor. 40: 221-255. Stover, L.E. 1964. Cretaceous ephedroid potlen froth West Africa. Micropaleontology 10: 145-156. Trevisan, L. 1980. Ultrastructural notes and consideration on Ephedripites, Eucommiidites and Monosulcites polen grains from Lower Cretaceous sediments of
Cretaceous Ephedroid Pollen southern Tuscany (Italy). Pollen Spores 22 : 85-132.
Wodehouse, R.P. 1935. Pollen Grains. Their Structure, Identification and Significance in Science and Medicine. McGraw-Hill, New York, NY, 578 pp. Zavada, M.S. 1984. Angiosperm origins and evolution based on dispersed fossil gymnopserm pollen ultrastructure. Ann. Mo. Bot. Gard. 71: 444-463. Zavada, M.S. 1990. The ultrastructure of three monosulcate pollen grains from the Triassic Chinle Formation,
western United States. Palynology 14: 41-51. Zavada, M.S. and Gabarayeva. 1991. Comparative pollen wall development of We/witschia mirabi/is and selected primitive angiosperms. Bull. Torrey Bot. Club 118 : 292-302,
(Received September 26, 1994: Accepted November 5, 1994)
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