Shaolin Zheng

A new species of osmundaceous fern rhizome, Ashicaulis macromedullosus sp. nov., from the Middle Jurassic, northern China

ABSTRACT Ashicaulis macromedullosus sp. nov. (Osmundaceae) is described on the basis of one silicified rhizome, collected from the Middle Jurassic Tiaojishan Formation in Hebei, China. This specimen consists of a small, upright stem surrounded by frond bases, and adventitious roots. The stem consists of pith, xylem cylinder, a two-layered cortex and petiole bases. In cross section, the stem has a dictyoxylic xylem cylinder composed of 24–32 xylem strands separated by many leaf gaps with some incomplete leaf gaps. This species is characterized by continuous cylindrical phloem, absence of medullary traces in the pith, no sclerenchyma in leaf trace concavity, homogeneous cortical sclerenchyma, and one mass of sclerenchyma in each stipular wing. This is the third structurally preserved rhizome of Ashicaulis from the Mesozoic in northern China and adds to the knowledge of fern diversity in China. Northern Hemisphere species from the Jurassic have a tendency to larger stele diameter than comparable Mesozoic species in the Southern Hemisphere.

New discovery of fossil cycad-like plants from the middle Jurassic of West Liaoning, China

The Cycadales are one of the most ancient lineages ofseed plants, with a fossil record that extends over 250 mil-lion years. Cycads are believed to have originated fromthe Late Palaeozoic, and reached its maximum diversityand distribution during the Mesozoic; however, their evo-lutionary history has remained relatively poorly under-stood[1―4].

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.

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.