Zikun Jiang

Ashicaulis beipiaoensis sp. nov., a New Osmundaceous Fern Species from the Middle Jurassic of Liaoning Province, Northeastern China

A new structurally preserved fern rhizome species, Ashicaulis beipiaoensis (Osmundaceae), is described from the Middle Jurassic Tiaojishan Formation in Beipiao City, Liaoning Province, northeastern China. The rhizome, with a maximum diameter of 4.0–4.5 cm, is composed of a homogeneous parenchymatous pith, an ectophloic-dictyoxylic siphonostele, a two-layered cortex, and a mantle of adventitious roots and petiole bases. The xylem cylinder consists of 13–16 xylem strands. The petiole base is characterized by a homogeneous sclerotic ring and a crescent-shaped sclerenchyma mass in the vascular bundle concavity. One large homogeneous sclerenchyma mass, accompanied by several smaller thick-walled fiber clusters, occurs in the petiolar stipular wings. Comparisons of anatomical features suggest that A. beipiaoensis sp. nov. shows distinct differences when compared to previously reported fossil and living osmundaceous taxa but bears close similarities to Osmunda shimokawaensis from the Middle Miocene of Hokkaido, Japan. The new species and O. shimokawaensis may represent an extinct branch in the Osmundaceae evolutionary tree. The fossil species of A. beipiaoensis provides further information for understanding the development and geological occurrences of osmundaceous rhizomes in the Northern Hemisphere.

A specialized new species of Ashicaulis (Osmundaceae, Filicales) from the Jurassic of Liaoning, NE China.

A new species of structurally preserved fern rhizome, Ashicaulis plumites (Osmundaceae, Filicales), is described from the Middle Jurassic Tiaojishan Formation in western Liaoning Province, NE China. The new species is characterized by a peculiar sclerenchyma mass in the petiolar vascular bundle concavity. This sclerenchyma mass varies from a linear-shape to a mushroom-like shape with a remarkable outward protuberance, which distinguishes the present new species from other Ashicaulis species. Such a protuberance is very rare among osmundaceous ferns, and should represent a unique type for sclerenchymatous tissue in the osmundaceous vascular bundle concavity. Recognition of the peculiar structure of this new fossil species enriches anatomical diversity of permineralized osmundaceous ferns, indicating that the family Osmundaceae might have experienced a remarkable diversification during the Middle Jurassic in NE China. The new species show anatomical similarities to Osmundapluma Miller from the Palaeocene of North America. The occurrence of A. plumites in the Middle Jurassic of China provides a new clue for understanding the evolution of some members of the living subgenus Osmunda.

New records of Jurassic petrified wood in Jianchang of western Liaoning, China and their palaeoclimate implications

Diverse and rich fossil wood records have been documented from the Mesozoic of Liaoning Province, NE China. The Tiaojishan Formation (mainly distributed in Beipiao, Chaoyang, Fuxin and Jianchang regions) is one of the most significant horizons for the Jurassic petrified wood in Liaoning Province. Previously, wood fossils of this formation were mainly reported in Beipiao and Chaoyang regions, whereas fossil wood record was merely known in Jianchang region. Here we describe new fossil wood specimens from the Tiaojishan Formation in Jianchang County, western Liaoning. Two fossil wood taxa, i.e., Protaxodioxylon jianchangense Tian et Wang sp. nov. and Xenoxylon peidense Zheng et Zhang were recognized on the basis of anatomical features. These fossil wood records add new data for understanding the fossil wood diversity, floral composition and palaeoclimate of the Tiaojishan Formation. The occurrence of Xenoxylon and Protaxodioxylon implies a cool temperate, wet and seasonal climate condition with interannual variations during the Middle to Late Jurassic transition in western Liaoning region.

A Jurassic wood providing insights into the earliest step in Ginkgo wood evolution

The fossil record of Ginkgo leaf and reproductive organs has been well dated to the Mid-Jurassic (170 Myr). However, the fossil wood record that can safely be assigned to Ginkgoales has not yet been reported from strata predating the late Early Cretaceous (ca. 100 Myr). Here, we report a new fossil wood from the Mid-Late Jurassic transition deposit (153–165 Myr) of northeastern China. The new fossil wood specimen displays several Ginkgo features, including inflated axial parenchyma and intrusive tracheid tips. Because it is only slightly younger than the oldest recorded Ginkgo reproductive organs (the Yima Formation, 170 Myr), this fossil wood very probably represents the oldest bona fide fossil Ginkgo wood and the missing ancestral form of Ginkgo wood evolution.

Investigation of Controlling Factors for Growth in Stromatolites of the Tieling Formation, Jixian, Tianjin

The Yan–Liao Aulacogen is located in the northern SinoKorean Plate, buried under huge Meso–Neoproterozoic sedimentation, and is widely distributed in Beijing, Tianjin and Hebei. In these strata, several microbial mats occur, represented by four stromatolite assemblages within the Upper Precambrian stratotype section at Jixian, Tianjin. Stromatolites developed in the Mesoproterozoic strata of North China can provide good materials for investigating the controlling factors of their growth. Our projects targeted the Tieling Formation stromatolites in Jixian of Tianjin in order to investigate their growth control factors. The Tieling Formation is located about 500 m east of Xiaolingzi Village, Jixian, Tianjin, and bears diverse stromatolites of perfect shape.

The Relationship between Phototropism and Plate Motion

Plant phototropism means that trees on the side directly exposed to sunlight generally grow faster than those on the opposite, and positive phototropism is easy to observe in crown and trunk. In this study, we chose the transverse section of tree trunk to observe. The definitive intensity of plant phototropism ranges regularly from strong to weak and finally disappeared along with the latitudinal change from high to low. In the well-preserved in-situ petrified wood phototropism phenomenon also exists. Different plates have different tectonic movements. Some rotated during certain geological time, which recovered from the palaeomagnetic records. The eccentricity of tree growth rings should be related to the direction of sunshine. In addition, we compared the phototropism direction of the trunk of the fossil wood with the living normal growth stumps, thus verifying the paleomagnetic evidence whether the plates rotated or not.

The Phototropism of Jurassic Petrified Wood in North China Plate

Trees on the side directly exposed to sunlight generally grow faster than on the opposite side, a phenomenon termed plant phototropism. There are in situ vertical trunks of silicified wood in the Xiadelongwan area of Yanqing County, north Beijing, where the first National Geologic Park of Petrified Wood of China has been built since 2002. A few trunks have well-preserved growth rings. One petrified stump from the formation shows a positive phototropism direction of SW230°. As compared with the modern normal growth stumps in Beijing plain area, which have a positive phototropism direction of SW210 ° ± 5°, the evidence of wood phototropism supports the conclusion of previous palaeomagnetic studies that the North China Plate has rotated clockwise since the Late Jurassic. The known petrified wood stumps in the Yanshan-Liaoning area are mainly found from the strata of 165–136 Ma, which corresponds to the main stage of the Yanshanian Movement.