Jehol Biota: In North China and South China

The Jehol biota is one of the most representative terrestrial biotas of the Early Cretaceous in East Asia, and its insect fossils are particularly notable for their high diversity and abundance. The core region of the Jehol biota is located in western Liaoning and also includes northern Hebei and southeastern Inner Mongolia. It is preserved in the Zhangjiakou-Dabeigou, the Yixian, the Jiufotang formations from bottom to top, and their correlated strata. The generalized Jehol biota extends to northwestern, central, and southeastern coastal regions of China, and may also include parts of neighboring countries in northeastern Asia. Generally, the Jehol biota in northeastern and northwestern China occurs at similar latitudes, and their fossil assemblages may exhibit similarities. However, whether representative species occur in southeastern China remains uncertain. In eastern Zhejiang, the stratigraphic framework of the Shouchang area is broadly comparable to that of western Liaoning. The Laocun Formation is roughly contemporaneous with the Zhangjiakou-Dabeigou Formation, while the Shouchang Formation is comparable in age to the Yixian Formation. Insect fossils from the Laocun Formation are relatively poorly known. A large number of insect fossils have been discovered from the Shouchang Formation, with species such as Vulcanicorixa dorylis (Hemiptera, Corixidae) being representative. Although some mayfly nymphs have been found in the Shouchang Formation, it seems that they do not belong to the representative species Ephemeropsis trisetalis from the Jehol biota. The insects from the Shouchang Formation display distinct regional characteristics and they are clearly different from those of the core Jehol biota, and no convincingly same species have yet been reported. Late Jehol biota fossil assemblages in eastern Zhejiang have been reported from the Chawan Formation, with an absolute age of approximately 120 Ma. The plant, insect, and fish fossils from this formation also differ significantly from those of the Jiufotang Formation. In summary, although the Early Cretaceous tectonic setting and stratigraphic framework in eastern Zhejiang are comparable to those of the Jehol biota in Yanliao region, the biotic assemblages differ markedly, reflecting ecological differentiation across regions at different latitudes during the same time interval.