Secrospiroxylon tolgoyensis gen. nov. et sp. nov., a unique coniferous stem from the uppermost Permian of the South Gobi Basin, Mongolia, and its palaeoclimatic, palaeoecophysiological, and palaeoecological implications

A permineralised tree stem, Secrospiroxylon tolgoyensis Y.CAI, H.ZHANG et FENG gen. nov et sp. nov., is described from the uppermost Permian in the Tsaagan Tolgoy section of the South Gobi Basin, Mongolia. The coniferous stem is unique for combining a heterocellular pith, an endarch primary xylem, and a Prototaxoxylon-type secondary xylem. Growth rings are inconspicuously present in the studied stem, whereas false rings are commonly present throughout the secondary xylem, indicating ecophysiological anatomical responses to continuous environmental turbulence under indistinctive seasonal climatic conditions during the latest Permian. Arthropod wood borings with two coprolite classes are recognised, speculated to originate from detritivorous oribatid mites. In addition, fungal hyphae and white-rot decay structures are commonly identified in the stem. Our study provides novel information on the diversity of the Angaran flora and additional information on climatic and environmental fluctuations, as well as fungus-plant-arthropod interactions in the terrestrial ecosystems of the latest Permian of southern Mongolia.