title: An integrative approach to understanding bird origins.
abstract: Recent discoveries of spectacular dinosaur fossils overwhelmingly support the hypothesis that birds are descended from maniraptoran theropod dinosaurs, and furthermore, demonstrate that distinctive bird characteristics such as feathers, flight, endothermic physiology, unique strategies for reproduction and growth, and a novel pulmonary system originated among Mesozoic terrestrial dinosaurs. The transition from ground-living to flight-capable theropod dinosaurs now probably represents one of the best-documented major evolutionary transitions in life history. Recent studies in developmental biology and other disciplines provide additional insights into how bird characteristics originated and evolved. The iconic features of extant birds for the most part evolved in a gradual and stepwise fashion throughout archosaur evolution. However, new data also highlight occasional bursts of morphological novelty at certain stages particularly close to the origin of birds and an unavoidable complex, mosaic evolutionary distribution of major bird characteristics on the theropod tree. Research into bird origins provides a premier example of how paleontological and neontological data can interact to reveal the complexity of major innovations, to answer key evolutionary questions, and to lead to new research directions. A better understanding of bird origins requires multifaceted and integrative approaches, yet fossils necessarily provide the final test of any evolutionary model.
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, PR China. xu.xing@ivpp.ac.cn.
authors.forename: Xing
authors.initials: X
authors.lastname: Xu
authors.affiliation: Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, PR China.
authors.forename: Zhonghe
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Dudley
authors.affiliation: Cancer and Developmental Biology Laboratory, Center for Cancer Research, NCI-Frederick NIH, Frederick, MD 21702, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Mackem
authors.affiliation: Department of Pathology, University of Southern California, CA 90033, USA. Cheng Kung University, Laboratory for Wound Repair and Regeneration, Graduated Institute of Clinical Medicine, Tainan, 70101, Taiwan.
authors.forename: Cheng-Ming
authors.initials: CM
authors.lastname: Chuong
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL 32306-4295, USA.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Erickson
authors.affiliation: Earth Sciences, Montana State University, Bozeman, MT 59717, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Varricchio
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000033:anatomy & histology / Q000145:classification / Q000502:physiology; D025061:Dinosaurs / Q000145:classification; D005241:Feathers / Q000033:anatomy & histology; D005260:Female; D005426:Flight, Animal; D005580:Fossils; D008297:Male; D009024:Morphogenesis; D010802:Phylogeny; D012098:Reproduction; D012137:Respiratory System / Q000033:anatomy & histology; D014921:Wings, Animal / Q000033:anatomy & histology