New Early Cretaceous Insects from Northwest China and Their Stratigraphic Implications

Apr 17, 2014     Email"> PrintText Size

In the Jiuquan Basin, Gansu Province, northwestern China, the Lower Cretaceous Xinminpu (Xinminbao) Group consists of the Chijinpu (Chijinbao), the Xiagou and the Zhonggou formations in ascending order. Abundant insect fossils have been discovered in these strata since 1947 when the giant mayfly Ephemeropsis trisetalis Eichwald was discovered in the Jiuquan Basin. Typical components of the Jehol Biota have been reported from this basin, including Coptoclava longipoda, E. trisetalis and Lycoptera. Although these strata have been studied for a long time, their age is still in dispute. During the past ten years, Professor ZHANG Haichun and his research group from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences have investigated these strata in Jiuquan and collected abundant insect fossils from the Xiagou and Zhonggou formations. 

Recently, under the guidance of Professor ZHANG Haichun, Mr. ZHENG Daran firstly reported several caddisfly cases and abundant adults of the dragonfly Hemeroscopus baissicus Pritykina in the Zhonggou Formation. Wings of dragonfly H. baissicus 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 dragonfly H. baissicus was widely distributed in the Lower Cretaceous of eastern Asia, and has been recovered from the Zaza Formation of Baissa in Transbaikalia, Russia, the Dzun-Bain Formation of Bon-Tsagaan in western Mongolia, the Lushangfen Formation of western Beijing and the Zhonggou Formation of Jiuquan in China, and the Dongmyeong Formation of Banryong-ri in southern Korea. Based on the existing records of H. baissicus, 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. 

This research was supported by Chinese Academy of Sciences, National Basic Research Program and the National Natural Science Foundation of China. 

The paper was published in Cretaceous Research (Zheng Daran, Zhang Haichun, Zhang Qi, Li Sha, Wang He, Fang Yan, Liu Qing, Jarzembowski E.A., Wang Bo, 2014.The discovery of an Early Cretaceous dragonfly Hemeroscopus baissicus Pritykina, 1977 (Hemeroscopidae) in Jiuquan, Northwest China, and its stratigraphic implications. Cretaceous Research. doi:10.1016/j.cretres.2014.02.020). 

  

Outcrop and insect fossils from the Jiuquan Basin. (Image by NIGPAS)

  

Distribution and suggested spread of Hemeroscopus baissicus Pritykina in the Early Cretaceous. (Image by NIGPAS)