Bennettitales And Cycadales From Lower Cretaceous Changcai Formation In Yanbian Area Of Jilin

The Lower Cretaceous Changcai Formation is distributed mainly in Laotougou and Tuntianying of Yanji County; Changcai, Fudong, Nanyang, Tushanzi, Songxiaping and Dajinchang of Helong County in eastern Jilin, NE China. It is an important coal-bearing strata consisting mainly of gray sandstone, sandy conglomerate and gray-green conglomerate intercalated with black shale, carbonaceous mudstone and coal beds, yielding abundant fossil plants. The author had been ongoing geological investigation of the Lower Cretaceous Changcai Formation in Changcai Coal Mine of the Helong County during 2003～2004 and collected lots of Bennettitales and Cycadales leaf fossils from the Changcai Formation of Changcai Coal-Mine, including more than 30 specimens of Bennettitales and 50 specimens of Cycadales. The fossils are mainly compressions in preservation with cuticles. Bennettitales and Cycadales fossils of the Changcai Formation recorded by previous authors are 15 species of 5 genera totally. They are: Bennettitales: Pterophyllum liaoningensis, Pt. jixiensis, Pt. cf. subschanense, Nilssoniopteris cf. prynadae, Tyrmia sp.; Cycadales: Nilssonia sinensis,N. angustissima, N.compta, N. orientalis, N. cf. shuangyashan, Nilssonia cf. sinensis, Nilssonia sp., Ctenis changcaiensis, Ct. chinensis, Ct. sp.; and Cycadophytes incertae sedis: Macrotaeniopteris califonica, Taeniopteris sp., based on the gross morphological characters of leaves. Under cuticular study of leaf compression fossils, 5 species of Bennettitales and 6 species of Cycadales are recognized from the Lower Cretaceous Changcai Formation in Yanbian area, eastern Jilin, China. They are as following: Bennettitales Nilssoniopteris prynadae Samylina Nilssoniopteris platyrachis (Samylina) comb. nov. Nilssoniopteris longifolia Doludenko? Nilssoniopteris sp. Neozamites verchojanensis Vachrameev Cycadales Nilssonia grossinervis Prynadae Nilssonia sinensis Yabe & ?ishi Nilssonia cf. schaumburgensis (Dunker) Nathorst Ctenis chinensis HsüCtenis lyrata Lee et Yeh Ctenis sp. All the materials are prepared as following: (1) Select the materials and cut one piece of well preserved materials from specimen use the small knife. (2) Macerate the small materials consequently in HCl, HF and Schulze's Solution until the materials change into yellow-brow corlor. (3) Dissolve the organic substances with NH4OH (about 5%), and separate cuticles with operating needles under binocular stereomicroscope. (4) Prepare slices for optical microscopic observation and photographing, or mount on the stub and coated with gold for SEM observation and photographing. Vachrameev (1990) had divided the Early Cretaceous floras all over the world into four floristic regions. Two regions are related in China, e.g. the Siberian-Canadian Region and the Euro-Sinian Region. The present research area is in the Siberian-Canadian Region. The author analyzed the distribution of Bennetitales and Cycadales from the Early Cretaceous Changcai flora, and found that all the species are within the Siberian-Canadian Region. Up to now, about 80 species of 37 genera were found from the Early Cretaceous Changcai Formation, including Bryophyte, Lycopsidiales, Equisetales, Ferns, Bennettitales, Cycadales, Ginkgoales and Conifers.Among them,living Bryophyte,Lycopsidiales, Equisetales and Ferns,mainly live in humid environment near the water. The existence of taxa indicate that the climate the Early Cretaceous Changcai formation might be humid. Living Cycadales is limited warm and humid tropical and subtropical climate zone, the presence of Bennettitales and Cycadales shows that the climate of Early Cretaceous might be warm also. Wild distributions of Ginkgoales has been reported from Tianmu Mountain of Zhejiang, China, where the climate warm and humid belongs to temperate in nature. The mean annual temperature is 8.8~14.8℃. The abundance of Ginkgoales associated with diversified conifers and Ceakonowskiales appers to indicate the the Early Cretaceous climate as temperate in the localities of Changcai flora. The palynological assemblage of the Early Cretaceous Changcai Formation consists of gymnosperm pollen and fern spores. The dominated taxa are Schizaeoisporites, Gleicheniidites, Lygodiumsporites, Cyathidites, Picea, Pinusand, Podocarpus, which indicate a humid and warm temperate climate. while r the content of Classopllis which indicate a arid environment is only 3%. Therefore the megofossil and palynological assemblages of the Early Cretaceous Changcai Formation would indicate a humid and warm temperate climate. The xeromorphic features Sumarized by Watson of Wealden gymnosperms, (mainly cycads and ginkgoales) (1)A thick-walled epidermis and hypodermis covered by a dense waxy cuticle with cutinization extending to the inner periclinal walls of the epidermis. (2)A cuticle of 5μm or more (3)Sunken stomata,papillate subsidiary cells. (4)presence of papillae and trichomes. The cuticular materials of the Early Cretaceous Changcai Formation show that some arid or semiarid climates.Such as the anticlinal cell walls cutinized and periclinal with flat papillaes and trichomes, stomata sunken. The climate of Early Cretaceous Changcai Formation is humid and warm temperate with seasonal aridity. Systematic Description: GymnospermaeBennettitales Nilssoniopteris Nathorst, 1909 Nilssoniopteris platyrachis comb. Nov. (pl.I,figs2,3;pl.VI,figs.3-6;pl.VII,figs.1-2; text-fig.2-B) Specimens: JLC030203A,B Description: Leaves lanceolate, about 80 mm long and 34 mm wide in presevation. Rachis 2-3mm wide. Membrane of lamina thick, margin entire, bearing on the surface of rachis, only few of its width exposed above. Vein sparse,arising at angle of 80°to rachis. Vein simple but fork once occasionally or fork once then close.It is about 1mm width between adjacent vein,vein at a concentration of 10-11 per 10 mm in margin of lamina. Epidermal hypostomatal, Upper cuticle thinner ,internal view showing the part correspond to zones of veins and between veins.Zones of narrower cells composed of 3-4 rows of moderate elongated cells,90 μm wide;Anticlinal cell walls ? shape of undulation,periclinal cell walls coarse. Areas of adjacent zones of narrower cells rather wide, composed of nearly oval or irrigular cells; Anticlinal cell wall U or V shape of undulation,with cutinized thickings ,periclinal cell wall irregularly cutinized , few base of trichomes and flattish papillae present.External of cuticle coarse, showing irregular sunken pits. Lower cuticle thicker. Internal view showing stomatal zones and no-stomatal zones. No-stomatal zones 300 μm wide, cells irregular or oval, about 30-35 μm in size.Anticlinal cell wall ? or U shape of undulation, cutinized, periclinal cell wall flat but finely mottled.Width of stomatal zones over 670 μm.Stomatal apparatus Bennettitalean,irrigularly in arrangenment, at a concentration of 60-70/mm2; Stomatal rectangular or oval,about(52-77) μm ×(44-57) μm in size. Stomatal pits variably oriented. Guard cells sunken, semicircle,15-35μm in size ;Cutinized thickenings at the stomatal pits and margin of guard cell. The polar appendage of guard cells nearly triangle or pentagonal, 7-10μm long and 4-8μm wide.Subsidiary cells width 1.5-2 times of guard cells, tetragonal or square-circle, outer margin cutinized.Suface of external flatter than upper,cavitys and pits also present.