中国科学院南京地质古生物研究所机构知识库

A silicified root, Amyelon bogdense Wan, Yang et Wang sp. nov., is described from the Changhsingian-Induan (?) Guodikeng Formation in south Taodonggou section, Turpan, Xinjiang Uygur Autonomous Region, northwestern China. The root consists of diarch protostele, primary xylem, secondary xylem, secondary phloem, and periderm. Primary xylem is exarch, with helical and scalariform thickenings on tracheidal walls. Secondary xylem is of the Agathoxylon-type, with alternately bi- to tetraseriate radial tracheidal pitting, uniseriate parenchymatous rays, and araucarioid cross-field pitting. Intercellular spaces occur between tracheids throughout the secondary xylem. Phloem is commonly compact. It is composed of radially aligned thick-walled cells, axial parenchyma and parenchymatous rays. Periderm consists of phelloderm, phellogen and phellem. Phelloderm cells are distributed external to the secondary phloem, with variable morphologies and sizes. Phellogen cells are commonly tabular and occasionally elongate. Phellem is distributed to the exterior of the phellogen, and is composed of 2-7, commonly 3-4 layers of radially arranged brick-shaped cells. Rootlets are elliptical to circular, less than 4 mm in diameter. Anatomical structures of rootlet are similar to those of the root. The arrangement of secondary xylem shows wedge-shaped spokes. Spaces between the secondary xylem spokes are either empty or filled with parenchyma. Some of the roots and rootlets have lenticel-like convex bodies. Lateral roots show no particular arrangement but appear to have been borne on only one side of the primary root. This is the first detailed report of the root anatomy with xylem and bark from the upper Paleozoic of the subangaran phytoprovince. The anatomical features differ from those of the previously studied stems in northwestern China, and provide additional information on the diversity of the subangaran flora. (C) 2019 Elsevier B.V. All rights reserved.