First record of the Mesozoic gymnosperm Xenoxylon Gothan in the Lower Cretaceous of northwestern China: New insights for its global paleobiogeography

Fossil wood serves as a crucial proxy for understanding terrestrial vegetation composition and reconstructing continental paleogeography throughout Earth’s history. The notable gymnosperm wood, Xenoxylon Gothan, is commonly found in the Mesozoic deposits across the Northern Hemisphere. In China, about 80 occurrences of this genus are documented in the eastern regions. However, limited occurrences are so far reported in the Mesozoic deposits of western China. Here, we describe new fossil wood specimens from the Lower Cretaceous of the Jiuquan Basin in Yumen City of Gansu Province, northwestern China. The fossils are characterized by the distinctive anatomy of Xenoxylon, including xenoxylean radial tracheid pitting and window-like cross-field pitting. Based on the characters of radial tracheid pits, cross-field pits, and ray heights, the fossils are recognized as Xenoxylon meisteri Palibin et Jarmolenko. To better understand the paleobiogeography of the Mesozoic Xenoxylon, a global survey of its occurrences is carried out, which reveals that Xenoxylon expanded its range both towards higher and lower latitudes from the Triassic to the Jurassic, then reduced its range northward in the Cretaceous. The results of this study corroborate that Xenoxylon-type trees were more likely to inhabit higher latitudes of the Northern Hemisphere (>30° N).