内蒙古霍林河盆地早白垩世植物化石

EARLY CRETACEOUS FOSSIL PLANTS FROMHUOLINHE BASIN IN INNER MONGOLIA

本文研究了内蒙古霍林河盆地霍林河组下含煤段的植物化石,共鉴定了21属36种。植物组合以蕨类占优势,银杏类、苏铁类和松柏类均有一定比例,同海拉尔盆地大磨拐河组所含植物组合成分相似。地层对比表明,霍林河组与海拉尔盆地的大磨拐河组和伊敏组可以对比,也能同阜新盆地的沙海组和阜新组对比。植物组合成分及地层对比都表明该植物组合时代为早白垩世早期。本文还描述了5个新种: Coniopteris huolinhensis sp.nov,Cladophlebis neimengensis sp.nov,pterophyllum huolinhense Sp.nov.pl.angustifolium Sp.nov,Nilssonia zelimunsia Sp.nov.

: The materials studied in this paper were collected from the lower part of the Huolinhe Formation in Huolinhe Basin, eastern Inner Mongolia. The flora is composed of 36 species in 21 genera including 5 new species, which are mainly: Equisetites hulunensis Ren, Acanthopteris gothani Sze, Coniopteris ermolaevii (Vassl.) Meng et Chen, C. huolinhensis sp. nov., Athyrium cretaceum Chen et Meng, Cladophlebis neimengensis sp. nov., Pterophyllum huolinhenese sp. nov., Pt. angustifolium sp. nov., Nilssoniopteris prynadae Samyl., Ginkgo digitata (Brongn.) Heer and Taxus sp.. According to the fossil plants and the stratigraphic correlation, the lower part of the Huolinhe Formation may be referred to early Early Cretaceous in age. Description of The New Species Coniopteris huolinhensis sp. nov. (P1. I, Figs. 3~7) Frond small, tripinnate. Rachis slender. Pinnae, pinnules and lobes of pinnules arising at variational angles which gradually becoming narrower from the lower position to the ultimate position of frond. Pinnule almost linear. Lobes splinter. Venation pinnate. One vein in each lobe. Feitile pinna independing or not, Sori elliptic, 1.5mm x 2mm. at the top of lobes. Indusium and sporange unknown. Spores triangular, 3 laesuraes, 40~ 60^m in diameter, Exine of spore thin and smooth, laesurae almost reaching the equator. This species differs from the known species: Coniopteris kolymensis, C. datungensis, C. setecea in the characters of gradual variations in form and its large sori. Cladophlebis nemengensis sp. nov. (P1, I, Fig. 14) Frond large, more than 35 cm long, bipinnate. Penultimate rachis up to 5mm wide, smooth. Ultimate pinnae rasing at 50~60 ?angles, alternate, lanceolate, 8 - 10cm long, 2~2.5cm wide. Pinnlues sickle form, 1.2 ~ 1.5cm long, 0.5 ~ 0.7cm wide. A few pinnlues lightly dissected, forming 1 ~ 3 oblate lobes. Venation pinnate, delicate, secondary nerves branching 2~3 times. The new species differs from Cladophlebis fuxinensis Meng and Cl. cf. gigantea Oishi. Pterophyllum huolinhense sp. nov. (P1. II.Figs. 1-5) Leaf oblanceolate, with a petiole, symmetric, 10 ~15cm long, widest up to 6cm. Rachis slender. Segments typically 2 ~ 3cm in length, 6 - 8mm in width, making angles of 75 ~ 80 to the rachis. Veins parallel, 9 ~ 16 in each segment, a few of them branching 1 time near the rachis. Upper cuticle thin, epidermal cells oblong, square or irregular, walls wave- like. Lower cuticle thin, longitudinally thickened cells showing the veins, cells in intervenular areas indistinct. Stomata on either lower or upper cuticles, particularly the former, making rows, elliptic in form, 20^m x 25/im. Guard cells slightly thickened. Subsidinary irregularly thickened. Trichome bases appearing frequently on both upper and lower cuticles, forming rows, elliptic, about 20^m in diameter. Pterophyllum liaoningense Meng et Chen is close to the new species, but stomata only occuring on its lower cuticle and its segments are longer and narrower than that of the new species. Pterophyllum angustifolium sp. nov. (P1. II, Figs. 6 - 10) Leaf oblanceolate, with a petiole, more than 13 cm long, 6cm wide. Rachis slender, smooth. Segments being opposite at the lower portion but alternate at the upper portion of leaf and making right angles to the rachis. Segments lineform, typically 3cm in length and 2mm in width, apex round, obviously contracting at the bases. Veins parallel, 4~6 in each egment. Epidermal cells on lower cuticle irregular, walls intensely sinuous. Cells on upper cuti-cle mainly square, oblong, wells slightly curved. Stomata circular, 30/im in diameter, in lower epiderm only, showing in rows, 3 ~ 4 rows in each intervenular area. Stomatal apparatus transverse or oblique to the veins. Guard cells arc like, thickened, Subsidiary cells wrapping the guard cells, irregular thickened.walls curved. The new species differs from Pterophyllum angustum, P. burejense and P. concinnum. Nilssonia zelimunsia sp. nov. (P1. I, Figs. 11 - 13) Leaf long ovate, 10cm long, 3.5cm wide. Rachis slender. Se