During the dinosaurs-birds transition, the most conspicuous morphological change is the abbreviation of the long bony tail. Due to the lack of transitional fossils, little is known about how that modification took place. In living birds, the tail ends in a compound ploughshaped element termed pygostyle that attaches the fan-shaped tail feathers, forming an indispensable flight apparatus. Based on comparative anatomical, histological and electrical scanning analyses, Wang et. al. suggested that the plough-shaped pygostyle and the tail fanning is evolutionally decoupled in the early avian history, which challenges the long-standing theory that these two features are coevolved. A plough-shaped pygostyle is distributed widely in Ornithuromorpha. Therefore, the rare occurrence of this structure in some enantiornithines is the result of convergence, as confirmed by a few other fossil birds, further highlighting that the early avian evolution is characterized by parallelism.
WANG Min
. A 130 million-year-old fossil bird indicates decoupled evolution of pygostyle and tail fanning[J]. Science & Technology Review, 2018
, 36(23)
: 26
-29
.
DOI: 10.3981/j.issn.1000-7857.2018.23.004
[1] Xu X, Zhou Z, Dudley R, et al. An integrative approach to understanding bird origins[J]. Science, 2014, 346(6215):1253293.]2] Wang M, Zhou Z H. The evolution of birds withimplications from new fossil evidences[M]//Maina J H. The Biology of the Avian Respiratory System. Heidelberg:Springer International Publishing AG, 2017:1-26.
[3] Gill F B. Ornithology[M]. New York:W. H. Freeman, 2007.
[4] Gatesy S M, Dial K P. From frond to fan:Archaeopteryx and the evolution of short-tailed birds[J]. Evolution, 1996, 50(5):2037-2048.
[5] Baumel J J. Functional morphology of the tail apparatus of the pigeon (Columba livia)[J]. Advances in Anatomy, Embryology, and Cell Biology, 1988, 110:1-115.
[6] Clarke J A, Zhou Z, Zhang F. Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of Yixianornis grabaui[J]. Journal of Anatamy, 2006, 208(3):287-308.
[7] Wang M, O'Connor J K, Pan Y et al. A bizarre Early Cretaceous enantiornithine bird with unique crural feathers and an ornithuromorph plough-shaped pygostyle[J]. Nature Communications, 2017, 8:14141.
[8] He H Y, Wang X L, Jin F et al. The 40Ar/39Ar dating of the early Jehol Biota from Fengning, Hebei Province, northern China[J]. Geochemistry, Geophysics, Geosystems, 2016, 7(4):Q04001.
[9] Vinther J. A guide to the field of palaeo colour[J]. Bioessays, 2015, 37(6):643-656.
[10] Zheng X, Wang X L, O'Connor J K et al. Insight into the early evolution of the avian sternum from juvenile enantiornithines[J]. Nature Communications, 2012(3):1116.
[11] Wang M, Li Z H, Zhou Z H. Insight into the growth pattern and bone fusion of basal birds from an Early Cretaceous enantiornithine bird[J]. PNAS, 2017, 114(1):1470-1475.