Morphological And Phylogenetic Study On New Materials Of Anchiornis From Jianchang,Western Liaoning, China

Recently, many small theropods have been discovered in western Liaoning, southeastern Inner Mongolia and northern Hebei of China. They show close relationship with avians. The discoveries reduce the gap between non-avian theropods and avians, thus provide distinct evidences in the evolution of feathers and the origin of bird flight. Anchiornis is such a theropod which was discovered from the Middle-Upper Jurassic Tiaojishan Formationin Yaolugou and Daxishan localities, Jianchang County, western Liaoing, China.Here I describe two new specimens of Anchiornis, HGM101 and HGM102, and compare them with other relevant species. This research revises the characters of Anchiornis as follows: sub-triangular skull in lateral view; the posterior border of external naris consisted with the maxillary process of premaxilla and the maxillary process of nasal; dorsoventrally flattened internarial bar; large sub-circular maxillary fenestra and sub-oval promaxillary fenestra; larchymal T-shaped in lateral view; sub-triangular antorbital fenestra; longitudinal groove along the dorsomedial margin of the slender sub-orbital ramus of the jugal; large paraquadrate foramen; distinct groove on the labial surface of the dentary housing the neurovascular foramina and the space between the foramina widening posteriorly; pneumatic foramen in the lateral surface of cervical vertebrae; about 28 caudal vertebrae; flat transverse process on the anteriormost caudals; distinct groove on the lateral surface of the middle caudal vertebrae; the middle and posterior chevrons bifurcated anteriorly and the length of the chevron about half of the relevant vertebrae; glenoid fossa laterally faced; acromial process not well developed; distal scapula slender and not distinctly extended; laterally located coracoid tubercle; short deltopectoral crest about one-fourth of the humeral length; ulna only slightly thicker than radius; distinct supracetabular crest, brevis fossa, cuppedicus fossa on the lateral surface of ilium; pubic peduncle of ilium wider than acetabulum and ischial peduncle; the shaft of pubis anteriorly sloped and the distal end of pubis strongly curved posteriorly; the length of tibiotarsus about 150% of the length of femur; the astragalus not fused with tibia; the ascending process of the astragalus parallelly rised and narrowed at the end; sub-arctometatarsalian metatarsals; MTI located at the disatal one-fourth of the MTII and not overturned; the second pedal ungual not distinctly large as a reaphook.The dataset for phylogenetic analysis includes 90 taxa and 374 characters from the researches reported before and data matrix from HGM101 and HGM102. The result of this study makes Anchiornis and Xiaotingia into a monophyletic group as a single clade within Deinonychosauria. Yet Archaeopteryx is still a member of Avialae.