地质学报（英文版）2005，Vol.79Issue(1)：7-10,4.
A Possible Long-tailed Bird with a Pygostyle from the Late Mesozoic Yixian Formation,Western Liaoning,China
A Possible Long-tailed Bird with a Pygostyle from the Late Mesozoic Yixian Formation,Western Liaoning,China
摘要
Abstract
An incomplete caudal vertebral series (IVPP V11309) from the Yixian Formation of late Mesozoic,Jianshangou area of B eipiao, western Liaoning Province, may represent a new bird. The tail is composed of at least 12 free caudal vertebrae and the most distal 5 caudal vertebrae co-ossified into a pygostyle. The pygostyle is plate-like and slightly curved dorsally. The anterior free caudals are amphiplatyan. The anterior caudal surfaces of the last three free caudals are concave, but their posterior articular surfaces are convex. The pygostyle is regarded as the first appeared flight apparatus during the evolutionary process from Archaeopteryx to neornithes. The pygostyle appeared in most early fossil birds and almost all the modern birds. Although their morphologies are different, they are basically formed by at least four last caudal vertebrae. The specimen V11309 is regarded as a bird rather than a non-avian theropod dinosaur based on the following characters: short caudal vertebrae, numerous pits present on the surfaces of the centra and, a foramen present between the basal part of the fused neural spines, which is similar to that of Struthio camelus. The discoveries of pygostyles from the therizinosauroids and oviraptorosaurs may provide strong evidence for supporting the origin of birds from small theropod dinosaurs. The structure of the pygostyle in specimen V11309 is different from those of Beipiaosaurus (Therizinosauroid) and Nomingia (oviraptorosaur). The most parsimonious interpretation is that these pygostyle-like structures are independently acquired by Beipiaosaurus and Nomingia during their evolutionary process.关键词
western Liaoning/Yixian Formation/late Mesozoic/pygostyleKey words
western Liaoning/Yixian Formation/late Mesozoic/pygostyle引用本文复制引用
L(U) Junchang,HOU Lianhai..A Possible Long-tailed Bird with a Pygostyle from the Late Mesozoic Yixian Formation,Western Liaoning,China[J].地质学报（英文版）,2005,79(1):7-10,4.基金项目
This work was supported by the Institute for the Study of Earth and Man at Southern Methodist University to L(u),J-C and China Geological Survey, Grant 200413000024. （u）
