Restudy On The Early Cretaceous Fish Fossils From Weichang Area,Hebei Province,North China

Northern Hebei is one of the classical regions for the study on Mesozoic terrestrial stratigraphy and Jehol Biota in China,with a history of more than 100 years.According to the data of predecessors,the Early Cretaceous strata are well developed and widely distributed in the Weichang area of Chengde City,yielding a lot of fossils of Jehol Biota,especially fishes and triopsids.Therefore,this thesis chooses the Weichang area as the key area to study the fossil fishes from the Early Cretaceous Jiufotang Formation and especially the fossil lampreys newly discovered in recent years.The Weichang area of Chengde City in Hebei province is the second important fossil site of the Early Cretaceous lampreys discovered in China after the Ningcheng County of Inner Mongolia.It is of great significance for the study on the ecological environments of Early Cretaceous Jehol Biota and living habits of fishes and the others.Lampreys are one of the oldest and most primitive jaw-less vertebrates,dating back to the Early Paleozoic Era.In geological history,the vertebrates without jaws had flourished in the Paleozoic Era,and later evolved to vertebrates with jaws.Finally they were replaced by vertebrates with jaws.Therefore,they are one of the most important components during the evolution of vertebrates.It is worth pointing out that although lampreys are ancient and primitive,and their morphological features are not changed much,they have gong through endless years of suffering and survived to today.Few lampreys have been found in China.The only known Early Cretaceous lampreys are Mesomyzon mengaegen from the the Yixian Formation in the Ningcheng County of Inner mongolia.There are totally 9well-preserved lamprey specimens unearthed from the Early Cretaceous Jiufotang Formation in the Weichang area of Chengde City for the thesis study,which were found by us during the fieldwork in 2021 and have been collected by the Museum of Earth Science of Hebei GEO University.According to my current study,those fossil lampreys can be assigned to two new genera and species.Because of the limited research time,only Hebeimyzon weichangensis gen.et sp.nov.and Hebeimyzon sp.(nov.)have been studied in this thesis paper.Based on the previous studies,this paper also deals with the other fossil fishes of the Jehol Biota from the Weichang area,such as Lycoptera davidi,L.sinensis,Protopsepharus liui and Peipiaosteus pani,and their morphological features are also briefly given herein.