47. Cuticle of Sagenopteris (Caytoniales), an Extinct Gymnospermous Plant, First Observed in Japan

No. 61 Proc. Japan Acad., 63, Ser. B (1987) 179

By Jong Heon KIM and Tatsuaki KIMURA TokyoGakugei University, Koganei, Tokyo 184 (Communicated by TeiichiKoBAYASHI, M.J. A., June 9, 1987)

The generic name of Sagenopteris has been applied to the leaves of the Caytoniales(or `Caytoniaplant') which is systematicallyan isolated Mesozoic gymnospermousclass on the basis of its fructification(see Thomas,1925; Harris, 1964). So far as we know, over 70 Sagenopteris species have been described from the Mesozoicplant-beds. However, it is difficultto make their specific identity only on the basis of their external morphology,unless they represent some remarkablefeatures. Their cuticular features, if available,are useful for makingtheir specificidentity to someextent, but knownSagenopteris species with cuticular features are not so many, becauseowing to the very thin and delicate character of their cuticles, it is difficultto make their cuticular preparations. This paper dealswith the first descriptionof cuticleof JapaneseSagenopteris leaflets preserved in the ammonite-nodulefrom the upper Lower Barremian KimigahamaFormation, Choshi Group, Chiba Prefecture. The present leaflets are, although not complete,referable to those of Sagenopteris inequilateralis Oishi knownfrom the Lower Cretaceousplant-beds in the Outer Zone of Japan.. Caytoniales GenusSagenopteris Presl, 1838: 164 Sagenopterisinequilateralis Oishi Figs. 1-9 Sagenopteris ? inequilateralis Oishi: Oishi, 1940, p. 363, pl. 47, figs. 3-5 (Lower CretaceousYuasa Formation, WakayamaPrefecture). Material: ISE-115 and other minor fragments of detachedleaflets. Description: 1) External morphology: Detailed descriptionswere already made by Oishi (1940,p. 363) and Kimura (1976,p. 196). 2) Cuticleof lamina: Cuticleis hypostomatic.Upper cuticle is thin, 1.5µm thick, consisting only of ordinary cells; cells are rhomboidalto pentagonal, typically 50 µm long and 33 µm wide, with straight and rather thick walls. Trichomeand papilla are absent. Lowercuticle is thinner than the upper, 1 µm thick, consisting of ordinallycells and stomatal complexes.Ordinary cells are hexagonalto polygonal,typically 54 µmlong and 36µmwide, with slightlysinuous wallswhich are sometimesjagged. Stomatalcomplex is haplocheilicand dicyclic. Stomata are irregularly scattered, 40-45 per square mm. Subsidiary and encircling cells are normallysix in number respectively. Guard cells are 42-46µm long and 24-27µm wide each, and are flush with the lower surface of lamina, but with slightly sunken region around the aperture irregularly oriented, surrounded by the non-specializedsubsidiary cells of which inner walls are contiguous, forming a circular `rampart'. Trichomes are rarely present but leavingonly their ring-shapedbase-scar, typically 19-27 µm in diameter. Papilla is not developed.No vein-coursecells are recognized. 18Q J. H. KIM and T. KIMURA [Vol. 63(B),

Figs. 1-9. Sagenopteris inequilateralis Oishi : 1: One of the detached and broken leaflets examined (ISE-115, collected by I. Obata). 2 : Upper cuticle of lamina, showing ordinary cells with straight and thick walls (slide no. JO 5-10) . 3 : Lower cuticle of lamina (inner view), showing ordinary cells and irregularly scattered stomata (SEM-photograph; slide no. 2302). 4: Ordinary cells with slightly sinuous lateral walls (inner view), enlarged from Fig. 3. 5 : Lower cuticle of lamina; a trichome base-scar is seen in its centre; ordinal cell-walls are slightly sinuous or jagged (slide no. JOS-04). 6: A dicyclic stoma (inner view) ; guard cells are enclosed by non-specialized subsidiary cells inside and encircling cells outside (SEM-photograph; slide no. 2304). 7: A model of stoma, drawn from Fig. 6 (A, aperture; G, guard cell; S, subsidiary cell; E, encircling cell). 8: Upper cuticle of petiolule; long and short ordinary cells are arranged in irregular longitudinal files (slide no. JOS-21). 9 : Lower cuticle of petiolule (slide no. JOS-22).

3) Cuticle of petiolule: Petiolule is rather thickly cutinized. Upper cuticle is 2.5 µm and lower one 2µm thick; cells are axially elongated, nearly rectangular to square, 29-58 µm long and 17-33 µm wide, with straight lateral walls and straight or oblique end walls, arranged in irregularly longitudinal files. Trichome is absent and papilla is not developed. No. 6] Cuticle of Sagenopteris inequilateralis 181

Discussion and comparison. We made detailed comparison of our cuticle with those of the following Sagenopteris species : S. hallei Harris, S. nilssoniana (Brongniart) Ward and S. serrata Harris (Harris, 1932, above-mentioned), S. mantelli Dunker (Carpentier, 1927, 1938), S. rhoif olia Presl (Daber, 1957, 1960), S. colpodes Harris and S. phillipsi (Brongniart) Presl (Harris, 1964, above- mentioned; Barnard and Miller, 1976, on the latter), S. heterophylla Doludenko et Svanidze (Doludenko and Svanidze, 1969), S. elliptica Fontaine, S. mclearni (Berry) Bell and S. williamsii (Newberry) Bell (LaPasha and Miller, 1985, above-mentioned) , S. liaoxiensis Shang et Wang and S. sp. cf. S. colpodes Harris (Shang and Wang, 1985) . However, none are similar in cuticular features to our present leaflets which are most characterized by the dicyclic stomatal complex. Of these above-mentioned Sagenopteris phillipsi is rather similar in form of ordinary cells of lamina and their well marked cell outlines, but it differs in having large-sized and elongate-lanceolate leaflets, thicker cuticles and isodia- metric lower ordinary cells not with sinuous walls but with straight walls. In addition to Sagenopteris inequilateralis, the following Sagenopteris species have been known from Japan (see Oishi, 1940; Huzioka, 1970) : S. nariwaensis Huzioka (Upper Triassic Nariwa Group), S. nilssoniana (Brongniart) Ward (Upper Triassic Yamanoi Formation and Nariwa Group and Lower Jurassic Kuruma Group), S. paucifolia (Phillips) Ward and S. sp. (Upper Jurassic Kuzuryu Group) and S. petiolata Oishi (Upper Jurassic Kiyosue Formation). They are all represented by leaf- or leaflet-impressions but are somehow dis- tinguishable from Sagenopteris inequilateralis in the form of leaflets. A broken leaflet illustrated by Nishida (1960, fig. 1-1) from the Choshi Group (exact horizon uncertain) as `unknown fragment of Pteropsida' belongs possibly to Sagenopteris inequilateralis on the basis of its venation. Generally Sagenopteris leaf bears two pairs of leaflets palmately on the top of petiole, but rarely one pair (Seward, 1910) or three pairs (Huzioka, 1970; Shang and Wang, 1985) and the leaflets of the lowest pair are usually inequilateral in form. Accordingly, our present leaflets and known leaflets of Sagenopteris inequilateralis are not always inequilateral as indicated by its specific name. We now think all the records of Sagenopteris inequilateralis (Oishi, 1940; Kimura, 1976; Kimura and Kansha, 1978) from the Lower Cretaceous plant-beds in the Outer Zone of Japan belong to the same plant. Acknowledgements. We express our sincere gratitude to Professor Emeritus Teiichi Kobayashi, M. J. A., of the University of Tokyo for giving us the facilities bo publish this paper. Our thanks are extended to Dr. Ikuwo Obata, Director of the Department of Geology, National Science Museum (Tokyo) who has provided the specimens kept at the museum on loan for the present study.

References

Barnard, P. D. W., and Miller, J. C. (1976) : Palaeontographica, B, 155, 31-117, pls. 1-15. Carpentier, A. (1927) : Mem. Soc. geol. du Nord. France, 10(1), 1-151, pls. 1-25. (1938) : Ann. Palaeont., 27, 155-179, pls. 1-12. Daber, R. (1957) : Geologie, 6(3), 306-315, incl. 3 pls. (1960) : ibid., 9(6), 591-637, incl. 15 pls. Harris, T. M. (1932) : Medd. om GrOnland, 85(5), 1-33, pls. 1-19. (1964) : The Yorkshire Jurassic Flora, II. Brit. Mus. (Nat. Hist.), viii+191 pp., 182 J. H. KIM and T. KIMURA [Vol. 63(B),

pls. 1-7. Huzioka, K. (1970) : Trans. Proc. Palaeont. Soc. Japan, N. S., no. 77, pp. 229-234, pl. 24. Kimura, T. (1976) : Bull. Natn. Sci. Mus. (Tokyo), C, 2(4), 179-208, pls. 1-6. Kimura, T., and Kansha, Y. (1978) : ibid., 4(4), 165-180. LaPasha, C. A., and Miller, C. N. Jr. (1985) : Palaeontographica, B, 196, 111145, pls. 1-16. Nishida, M. (1960) : Bull. Fac. Lit. Sci., Chiba Univ., 3(2), 187-193, pls. 1-3 (in Japanese with English description of new species). Oishi, S. (1940) : Journ. Fac. Sci., Hokkaido Imp. Univ., 4, 5(2-4), 123-480, pls. 1-48. Seward, A. C. (1910) : Fossil Plants, II. Cambridge Univ. Press, xxi+624 pp. Shang, P., and Wang, Z. Q. (1985) : Acta Palaeont. Sinica, 24(5), 511-517, pls. 1-3 (in Chinese with English abstract and description of a new species). Thomas, H. H. (1925) : Philos. Trans., London, 213B, 299-363, pls. 11-15.