A quantitative analysis of leaf life span reveals the Mesozoic significant gymnosperm Xenoxylon as evergreen: First evidence from the Early Cretaceous Jehol Biota in northeastern China

The Early Cretaceous Jehol Biota in western Liaoning Province of China and adjacent regions, is one of the most spectacular Mesozoic terrestrial lagerstaeurotten in East Asia. Diversified fossil wood has been reported for the last two decades for the Jehol Biota. However, little is known about the fossil wood from the Lower Cretaceous Jiufotang Formation in the Kazuo area of western Liaoning. Here, we report new fossil wood material from the Lower Cretaceous Jiufotang Formation in Kazuo County of western Liaoning Province, northeastern China with well-preserved xenoxylean radial tracheid pitting and window-like cross-field pitting. Due to a novel combination of radial tracheid pitting, cross-field pitting and ray height, a new species, Xenoxylon kazuoense Xie, Wang, Tian et D.Uhl sp. nov., is recognized here belonging to the gymnosperm. Based on the well-preserved tree growth rings, we first perform a quantitative analysis of leaf life span for the Mesozoic common gymnosperm Xenoxylon. The result shows the tree X. kazuoense sp. nov. was evergreen with a leaf retention time (LRT) of 3e15 years. The discovery of this new species leads to a further understanding of the biodiversity of fossil wood in the Early Cretaceous Jehol Biota and the leaf phenology of trees growing in this area during the Early Cretaceous. (c) 2023 Elsevier Ltd. All rights reserved.