Insights into the evolution of rachis dominated tail feathers from a new basal enantiornithine (Aves: Ornithothoraces)

摘要

We report on a new enantiornithine Eopengornis martini gen. et sp. nov. from the lowest horizon of the Jehol Biota in Hebei, China; dated at 130.7Mya, this is the second oldest avian bearing fossil deposit in the world, recording the First Appearance Datum of Enantiornithes. The new specimen, only the second enantiornithine and third bird reported from this horizon, preserves numerous synapomorphies with the largest Lower Cretaceous enantiornithine Pengornis houi from the Jiufotang Formation dated at 120Mya. Together, they form a new avian lineage that lasted over 10Myr, which is longer than any known clade of Lower Cretaceous enantiornithine. Eopengornis reveals new information about basal enantiornithine morphology such as the presence of a metatarsal V, helping to clarify the early evolution of these dominant Cretaceous avians. Furthermore, Eopengornis preserves a previously unrecognized tail morphology: a pair of elongate fully pennaceous rachis dominated feathers. This discovery confirms hypotheses proposing that the rachis dominated racket-plumes in basal birds represent modified pennaceous feathers. We suggest that the ornamental racket-plumes in enantiornithines and Confuciusornis evolved independently from the basal pygostylian condition, which we infer was a tail formed of normal flight feathers.(c) 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 805-819.C1 [Wang, Xiaoli; Zheng, Xiaoting] Linyi Univ, Inst Geol & Paleontol, Linyi 276000, Shandong, Peoples R China. [Wang, Xiaoli; Zheng, Xiaoting] Tianyu Nat Hist Museum Shandong, Pingyi 273300, Shandong, Peoples R China. [O'Connor, Jingmai K.; Wang, Min; Hu, Han; Zhou, Zhonghe] Chinese Acad Sci, Inst Vertebrate Paleontol & Paleoanthropol, Key Lab Vertebrate Evolut & Human Origins, Beijing 100044, Peoples R China.RP O'Connor, JK (reprint author), Chinese Acad Sci, Inst Vertebrate Paleontol & Paleoanthropol, Key Lab Vertebrate Evolut & Human Origins, Beijing 100044, Peoples R China.EM jingmai.oconnor@gmail.comFU National Basic Research Program of China (973 Program) [2012CB821906]; National Natural Science Foundation of China [41172020, 41372014]FX We thank Y. Li (IVPP) for preparing the specimen, S. Zhang (IVPP) for assistance with the histology, X-M. Zhang (STM) for assistance, and J. Zhang (IVPP) for photographing the specimen. This research was supported by the National Basic Research Program of China (973 Program, 2012CB821906), the National Natural Science Foundation of China (41172020, 41372014), and the Chinese Academy of Sciences. Data accessibility: the specimen STM24-1 is reposited in the collections of the Shandong Tianyu Museum of Nature, Pingyi, China.NR 45