New Finding Of Fossil Fishes From Jehol Group In Yixian County, Western Liaoning, With A Discussion On Its Biostratigraphy

New Fossil fishes, found from the Jehol Group (Late Jurassic-Early Cretaceous) in Wujiatun Village, Yixian County, western Liaoning, are described, and a re-description on "Lycoptera muroii" (Takai) and rearrangement of its systematic position, are made in this paper.The fish group discovered in Wujiatun Village is composed of chondrostei, amiids and teleostei fishes. Among them, two new species, Yanosteus boi sp.nov (chondrostei) and Jinanichthys major sp. nov. (teleostei), and two other species undetermined, Sinamia sp. (amiids) and Longdeichthys sp.( teleostei) are included.A detailed description on "Lycoptera muroii", which is only seen in Jingangshan and Zaocishan Villages, Yixian County, leads to a conclusion that the fishes should neither belong to Lycoptera suggested by Liu et al. (1963), nor belong to Asiatolepis as Takai (1944) did, but represent a new genus, Yixianichthys gen. nov. It is mainly characterized by its body form, dentary and a special type of scale.In this paper, the studies on late Mesozoic fossil fishes in North China is totally reviewed, and three fish assemblages are formally introduced, i.e., the Liaosteus assemblage, Peipiaosteus-Lycoptera-Protopsephurus assemblage andJinanichthys-Longdeichthys-Yanosteus boi assemblage in ascending order. The first assemblage represents a fish fauna found in Haifanggou Formation of Jurassic, and the late two assemblages show the fish climax in Jehol Fauna, though they represent two stages of the fish evolution in Late Mesozoic respectively.A comparison and discussion are also made on the relationship between the Mesozoic fish assemblages in West Liaoning and North Hebei, and the other part of China (include Jiuquanichthys fish group in Gansu, Siyuichthyids fish group in Xingjiang and Mesoclupea fish group in Zhejiang) and abroad (include Mesozoic fishes in Japan, Central Asia, England, Belgium and the famous Archaeopteryx-bearing Solnhlfen limestone). But up to now, the fish assemblages in North China are still not able to provide convincible evidences for the definition of the continental Jurassic-Cretaceous boundary in China.Systematic PaleontologyClass Osteichthyes Huxley 1880Subclass Actinopterygii Cope, 1887Superorder Chondrostei sensu Patterson 1982 ( Muller, 1844) Order Acipenseriformes Berg 1940Family Peipiaosteidae Liu et Zhou, 1965 Genus Yanosteus Jin et al., 1995Type species Yanosteus longidorsalis Jin et al.,1995Yanosteus boi sp.nov. (Figs.4-5; Pis.1-3) Etymology bo, Chinese pronunciation (pinyin) for the family name ofMr. Bo Haichen, the director of Yizhou Fossil Museum, Yixian County.Locality and Horizon Wujiatun Village, Yixian County, Liaoning Province; Jiufuotang Fm., Early Cretaceous in ageDiagnosis Yanosteus of middle size. Head about 1/5 of its total length; Body naked, with only one row of lateral line canal scales in both side. Internal bones are highly ossified; Base of dorsal fin broad, about 1/4 of total length of the fish; more than 10 pieces of ventral caudal fulcra.TeleosteiFamily Lycopteridae Cockerell 1925 Genus Jinanichthys Ma et al., 1988Type species Lycoptera longicephalus Liu et al. 1963Jinanichthys major sp.nov: (Figs.7-9; Pis. 4-7)Etymology major refers that the new species has a relative large size than the type species.Locality and Horizon Wujiatun Village, Yixian County, Liaoning Province; Jiufuotang Fm., Early Cretaceous in ageDiagnosis Jinanichthys of large size, with a total length reaching to 24cm. Head about 1/4 of the total length. Lower limb of preoperculum only a little short than upper limb of it. Supremaxilla large, about equal to maxilla in breath. Tooth undeveloped. Caudal fin with 15 forked fin rays in general.Yixianichthys gen.nov.Type species Asiatolepis muroii Takai, 1944Etymology Yixian, Chinese pronunciation (pinyin) for Yixian County, the fossil locality, oDiagnosis The new genus is characterized by its highly fusiform body, a dentary with co...