Leaf phenology and paleoclimatic and paleoenvironmental insights derived from Yiwupitys elegans of the Yiwu Jurassic Forest, Xinjiang, China

Many permineralized conifer stems and trunks have been documented from the Jurassic strata of the Xinjiang Uygur Autonomous Region (Xinjiang), Northwest China. Xylem anatomical studies have showed that these stems and trunks belonged to a diverse range of plants. However, the leaf phenology and the paleoclimatic and paleoenvironmental significance of these fossil plants have rarely been studied. We quantitatively analyzed the anatomical characteristics of a permineralized conifer stem—Yiwupitys elegans Gou et Feng 2023—from the Middle Jurassic Xishanyao Formation in northeastern Xinjiang, which has distinct and wide growth rings in the secondary xylem. Analyses of the Mean Sensitivity and Ring Markedness Index of the growth rings suggest that a stable paleoclimate with regular seasonal fructifications likely prevailed during the Middle Jurassic in this area. The statistical analyses of cell diameters and anatomical features of leaf traces in six successive growth rings indicate that this fossil plant was deciduous. Our study elucidates the ecophysiological characteristics of a Middle Jurassic conifer plant and provides new insights into the corresponding paleoclimate and paleoenvironment based on quantitative cellular analysis of the fossil stem.