Ning Tian

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.

Fertile structures with in situ spores of a dipterid fern from the Triassic in southern China.

Clathropteris was a typical dipterid fern with well documented fossil record and was widely dispersed during the Mesozoic; however, our knowledge of fertile structures including in situ spores for this genus is still very limited. Here we report well-preserved compression specimens of Clathropteris obovata Oishi from the Late Triassic of Guangyuan, Sichuan Province, China. The specimens show round to oval and exindusiate sori, vertical to oblique annuli in sporangia, and in situ trilete spores with verrucate and baculate sculptures, which are comparable to dispersed spore genera of Converrucosisporites and Conbaculatisporites. Comparisons of relevant fossil taxa suggest that specimens of C. obovata from Triassic of China provide for the first time in Asia the detailed fertile structures with in situ spore characters of dipterid fossil Clathropteris. Unlike living Dipteris, Mesozoic fossils of Dipteridaceae show a high diversity and a range of complex morphology of in situ spores, thus are significant for the evolutionary links between Dipteridaceae and other related fern clade, including Gleicheniaceae and Matoniaceae of the Gleicheniales.

Mesozoic non-marine petroleum source rocks determined by palynomorphs in the Tarim Basin, Xinjiang, northwestern China

The Tarim Basin in Northwest China hosts petroleum reservoirs of Cambrian, Ordovician, Carboniferous, Triassic, Jurassic, Cretaceous and Tertiary ages. The sedimentary thickness in the basin reaches about 15 km and with an area of 560 000 km 2 , the basin is expected to contain giant oil and gas fields. It is therefore important to determine the ages and depositional environments of the petroleum source rocks. For prospective evaluation and exploration of petroleum, palynological investigations were carried out on 38 crude oil samples collected from 22 petroleum reservoirs in the Tarim Basin and on additionally 56 potential source rock samples from the same basin. In total, 173 species of spores and pollen referred to 80 genera, and 27 species of algae and fungi referred to 16 genera were identified from the non-marine Mesozoic sources. By correlating the palynormorph assemblages in the crude oil samples with those in the potential source rocks, the Triassic and Jurassic petroleum source rocks were identified. Furthermore, the palynofloras in the petroleum provide evidence for interpretation of the depositional environments of the petroleum source rocks. The affinity of the miospores indicates that the petroleum source rocks were formed in swamps in brackish to lacustrine depositional environments under warm and humid climatic conditions. The palynomorphs in the crude oils provide further information about passage and route of petroleum migration, which is significant for interpreting petroleum migration mechanisms. Additionally, the thermal alternation index (TAI) based on miospores indicates that the Triassic and Jurassic deposits in the Tarim Basin are mature petroleum source rocks.

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.

Fires and storms???a Triassic???Jurassic transition section in the Sichuan Basin, China

The Upper Triassic Xujiahe and Lower Jurassic Zhenzhuchong formations of the Sichuan Basin, China, are important sources of plant fossils and windows into the intervening extinction event. However, there is an on-going debate as to whether the environment represented by the Xujiahe and Zhenzhuchong formations was continental or included an important marine component. We studied the Xujiahe–Zhenzhuchong section near Qili Town of Xuanhan County, in the east of the basin and report hummocky and swaley cross-stratification in the Xujiahe Formation. This, along with minor Skolithos and heterolithic bedding, provides strong evidence for shallow marine conditions and favours an interpretation as the deposits of a wave-dominated coast. It also suggests common and extreme storm activity, possibly hurricanes, at what was a mid-latitude (c. 34–40°N) location in the Late Triassic. Charcoal is found in most samples throughout the section. The predominant fossil wood morphology is consistent with Xenoxylon. Together, the sedimentological evidence of storms and fire suggests a highly disturbed environment.

Permineralized osmundaceous and gleicheniaceous ferns from the Jurassic of Inner Mongolia, NE China

Structurally preserved fossil ferns are extremely significant for exploring the origin and evolution of this plant clade; however, they are quite scarce and limited in the Mesozoic. Here, we report some well-preserved fern rhizomes and rachides with anatomical details from the Upper Jurassic Manketouebo Formation in Inner Mongolia, NE China. Two taxa, including Ashicaulis liaoningensis (Zhang et Zheng) Tidwell referred to Osmundaceae and Gleicheniorachis sinensis sp. nov. referred to Gleicheniaceae, are recognized. Anatomically, Ashicaulis liaoningensis consists of a heterogeneous pith, an ectophloic dictyoxylic siphonostele, a two-layered cortex, C-shaped leaf traces, and a mantle of petiole bases. The petiole base is characterized by a heterogeneous sclerotic ring with an abaxial thick-walled fiber arc. Gleicheniorachis sinensis sp. nov. consists of a C-shaped vascular bundle with two incurved adaxial hooks, a distinct sclerenchyma sheath, an endodermis, and a heterogeneous cortex. In particular, the finding of Gleicheniorachis sinensis sp. nov. represents the first report of unequivocal Jurassic record of Gleicheniaceae in northern China, as well as the first record of a Jurassic permineralized gleicheniaceous fern in the Northern Hemisphere. This study provides new data and evidence for exploring the anatomical diversity and evolution of Mesozoic ferns, and contributes to further understanding the floral composition of Late Jurassic flora in Northeast China.