Pterophyllum fossils from the Middle Jurassic Yaojie Formation, Gansu Province and its paleogeographical significance in China

Abstract

Pterophyllum, an extinct plant of Bennettitales, constitutes a significant component of the Mesozoic flora. In this study, we identified four fossil species of Pterophyllum from the Middle Jurassic Yaojie Formation in the Yaojie Basin and the Baojishan Basin in Gansu Province, Northwest China. Through analysis of macroscopic and macroscopic characteristics, these specimens were identified as Pterophyllum xinjiangensis Zhao, P. subaequale Hartz, P. ptilum Harris, and P. angustum (Braun) Gothan. These findings bridge gaps in the study of Bennettitales fossils in the region, affirming the warm and humid climate of the Yaojie Basin and the Baojishan Basin during the Middle Jurassic. Moreover, a comprehensive analysis of 598 reported Pterophyllum fossil records in China revealed that their occurrences from the Late Triassic to the Early Cretaceous was constrained by ancient climates and tectonic. The Late Triassic exhibited the highest diversity, with 83 species, which were widespread across warm-humid and tropical-subtropical zones in China; however, their diversity decreased sharply in subsequent periods, increased slightly in the Early Cretaceous, and then disappeared. In this paper, we further examined the habitat characteristics of this genera based on its spatiotemporal distribution and the paleogeographic and paleotectonic features of its origins, elucidating the coupled relationship between its distribution and ancient geographic and tectonic factors.