New record of Jurassic Xenoxylon wood from Gansu, northwestern China, and its palaeoclimatic implications

Fossil wood is a significant proxy for terrestrial palaeoclimate and palaeogeography. Abundant and diversified Mesozoic fossil wood has been documented in China. However, there are limited reports of Jurassic fossil wood records from northwest China. Herein, several calcified wood fossils are described in anatomical detail, from the Middle Jurassic (Bajocian to Callovian) Xinhe Formation in Gansu Province. They were identified as two species of the fossil wood genus Xenoxylon Gothan of Coniferales, namely X. latiporosum (Cramer) Gothan and X. peidense Zheng et Zhang. The newly collected material represents the first record of Jurassic petrified wood from Gansu Province. Based on the palaeoclimatic implication of Xenoxylon, we propose that the Baojishan Basin may have experienced a distinct short-term cooling during the Middle Jurassic. We analysed the fossil diversity and spatial-temporal distribution of Xenoxylon species in China. A total of 15 Xenoxylon species have been documented in China. These occurred from the Late Triassic to Late Cretaceous, but flourished from the Jurassic to Cretaceous intervals. Geographically, they are distributed across 13 provinces, mainly in northeast China. Significantly, this record expands the distribution of this important climate indicator taxon.