New Fossil Evidence Suggests That Angiosperms Flourished in the Middle Jurassic

Abstract

Angiosperms are a group of plants with the highest rate of evolution, the largest number of species, the widest distribution and the strongest adaptability. Needless to say, angiosperms are the most important group for the humans. The studies on the origin, evolution and systematics of angiosperms have been the major challenges in plant sciences. However, the origin and early history of angiosperms remains poorly understood and controversial among paleobotanists. Some paleobotanists insist that there were no angiosperms in the pre-Cretaceous age. However, this conclusion is facing increasing challenges from fossil evidence, especially Early Jurassic Nanjinganthus, which is based on over two hundred specimens of fossil flowers. Studying more fossil plants is the only reliable way to elucidate the origin and early evolution of angiosperms. Here, we document a new species of angiosperms, Qingganninginfructus formosa gen. et sp. nov, and provide the first detailed three-dimensional morphology of Qingganninginfructus gen. nov from the Middle Jurassic of Northwest China. A Micro-CT examination shows that the best-preserved fossil infructescence has eleven samaroid fruits, each with a single basal ovule. Since these fossils are distinct in morphology and organization from all organs of known gymnosperms and angiosperms (the latter are defined by their enclosed ovules), we interpret Qingganninginfructus as a new genus of angiosperms including a new species, Q. formosa gen. et sp. nov., and an unspecified species from the Middle Jurassic of Northwest China. The discovery of this new genus of angiosperms from the Middle Jurassic, in addition to the existing records, undermines the "no angiosperms until the Cretaceous" stereotype and updates the perspective on the origin and early history of angiosperms.