Zhuotingoxylon Liaoi Gen. Et Sp. Nov., a Silicified Coniferous Trunk from the Changhsingian (Permian) of Southern Bogda Mountains, Northwestern China

A silicified trunk, Zhuotingoxylon liaoi Wan, Yang, Wang, Liu et Wang gen. et sp. nov., is described from the uppermost part of Guodikeng Formation in South Taodonggou section, Turpan-Hami Basin, Xinjiang Uygur Autonomous Region, northwestern China. It is characterized by a solid pith, endarch primary xylem and pycnoxylic wood. The pith is composed of parenchyma and sclereids. Radial walls of primary xylem tracheids have spiral and scalariform thickenings. Secondary xylem consists of thick-walled tracheids and parenchymatous rays. Uniseriate rounded pits with oval apertures are distributed on radial tracheidal walls separately. Cell walls of rays are homogeneous and smooth. Rays are 1-10 cells high in tangential section. Cross-field pits are cupressoid. There are 1-4 bordered pits with slit-like to oval apertures in each cross-field. Based on the anatomical features of the pith and xylems, it is proposed that the new stem has a coniferous affinity. The new fossil stem adds to the knowledge of vascular plant diversity close to the Permian-Triassic boundary.