Research On A New Specimen Of Enantiornithine From Yixian Formation In Fengning County,Northeastern Hebei In China

In the last two decades,the fossils of feathered non-avian dinosaurs,stem birds,enantiornithes and Ornithuromorpha have been reported more and more.These fossils have provided a number of information for us to reveal secrets of the origin and evolution of birds and feathers and also the origin of bird's flight.Meanwhile,enantiornithes play an important role in research of issues as mentioned.The enantiornithes fossils found in the Jehol fauna of China account for 50% of the total number of bird fossils in Mesozoic and nearly complete skeletons are preserved.The discovery of hard-to-preserve structures such as fossils of feathers,follicular fossils,embryos fossils,ingested matter and juveniles fossils provides indispensable and direct evidences for the research on biological characteristics,ecological characteristics,flight ability and phylogeny of enantiornithes and even early birds.A new enantiornithes fossil from Lower Cretaceous Yixian Formation of Hebei Province in northeastern China is fully studied and classified into Liaoningornis.The method of CT scanning technology is used.By the method,the specimens flattened and embedded in surrounding rock are reconstructed in three dimension,and so as to observe the morphological characteristics of specimens to the maximum extent.Research progresses have been made on the functional significance of skeleton,development pattern,flight ability and habits of the fossil bird as it lived.The neossoptiles covering the whole body and imprint of feather on the wings provide the new data for understanding the origin of the feather and reveal the feather growth pattern of the early juvenile enantiornithines.Slender and long tail feather supports the hypothesis that feather is evolved from scales.The preserved bone features may indicate the living habits of the specimen before its death.Its curved claw joints and tiny teeth show its arboreal insectivorous habits.In this paper,the phylogenetic evolution of the specimen is analyzed on the basis of up to date morphological character matrix analysis,and the position in the phylogenetic evolution are discussed.In this dissertation,a detailed description of Liaoningornis which has remained controversial has been performed.At present,there is only one species belongs to Liaoningornis IVPP V 11303(1-2),named Liaoningornis longidigitrus.In addition,the specimens of juveniles Liaoningornis from Lower Cretaceous Dabeigou Formation of Hebei province in northeastern China has been described and discussed.Because of the specific sternum of Eoalulavis similar to studied specimen,it is speculated that the both of genera have interspecific relationship.The detailed morphological characteristics of Eoalulavis have been described and contrasted with Liaoningornis.At the same time,the previous indistinct judgment and question description about Eoalulavis and Liaoningornis have been revised.The studied specimen and early reported juveniles of enantiornithines from the Early Cretaceous in China have been compared in the dissertation.The comparative result shows that they have some common features,although they don't belong to the same family,which indicates the same morphological pattern in enantiornithines.The developmental pattern by the specimen supports the hypothesis of the evolution of enantiornithines.It provides information for the research about the postnatal development of the Cretaceous birds.The phylogenetic analysis shows that this taxon is located at the most basal position among all the known enantiornithines,and even more primitive than Protopteryx.Although its advanced morphological features are contrary to the result of system evolution analysis,it is further proved that the phylogenetic palingenesis phenomenon occurs in the process of enantiornithines development.