The discovery of an Early Cretaceous dragonfly Hemeroscopus baissicus Pritykina, 1977 (Hemeroscopidae) in Jiuquan, Northwest China, and its stratigraphic implications

The Early Cretaceous dragonfly Hemeroscopus baissicus Pritykina is reported for the first time from the Jiuquan Basin, Gansu Province, Northwest China based on adult wings. These wings are different from those from other localities in two aspects: the oblique crossvein ‘O’ is 3 or 4 cells distal of the subnodus; the wing size is much smaller (30–42 mm in length for forewings). These differences are considered to be intraspecific variations, based on which diagnoses of the genus Hemeroscopus and the family Hemeroscopidae are revised. The discovery of H. baissicus in Jiuquan suggests that the Zhonggou Formation may be correlated with the Fuxin Formation in Liaoning Province, the Lushangfen Formation in western Beijing, and the Dongmyeong Formation in southern Korea. A possible migration path of the dragonfly is indicated that it initially appeared in Transbaikalia in the Aptian, migrated southwestwards to Mongolia in the Aptian or early Albian, and then southwestwards to northwest China, southeastwards to northeast China, and southern Korea in the early Albian.