First records of Pinuxylon and Xenoxylon wood from the Cretaceous in Shandong Province, Northeast China

Abstract

Early Cretaceous petrified wood demonstrates remarkably high diversity across both northern and southern phytoprovinces in China. In recent years, an increasing number of fossil wood discoveries have been made in Cretaceous deposits throughout China, while current research on Early Cretaceous fossil wood remains primarily focused on the northeastern region. However, Cretaceous fossil wood occurrences remain exceptionally scarce in Shandong Province compared with other regions. This study reports the first discovery of well-preserved fossil wood from the Lower Cretaceous in the Jiaolai Basin, represented by two taxa, i.e., Pinuxylon shandongense sp. nov. and Xenoxylon latiporosum (Cramer) Gothan. Notably, P. shandongense sp. nov. constitutes the earliest fossil record of the genus Pinuxylon reported. Phenetic analysis of anatomical characters indicates that this new species is most closely related phylogenetically to P. pinastroides (Kraus) Stockmans et willière. Furthermore, anatomical examination of Xenoxylon latiporosum combined with growth-ring analysis of Keteleerioxylon shandongense indicates that the Jiaolai Basin experienced a seasonal climate during the Early Cretaceous, characterized by localized humid zones within a predominantly arid regime. These discoveries markedly expand the fossil records of Xenoxylon and Pinuxylon, providing unprecedented clarity regarding floristic assemblages in the ecotone between northern and southern phytoprovinces. They yield critical insights into both Mesozoic wood evolution and the paleobiogeography of Cretaceous fossil woods in East Asia. Furthermore, our reconstruction of Early Cretaceous paleoenvironments in the Jiaolai Basin, based on growth-ring analysis, establishes fundamental evidence for Cretaceous paleoclimatic reconstructions in this region.