Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour

Show simple item record Zheng, Xiaoting O’Connor, Jingmai K. Huchzermeyer, Fritz W. Wang, Xiaoli Wang, Min Zhou, Zhonghe 2013-05-03T10:16:35Z 2013-09-30T00:20:03Z 2013-03
dc.description.abstract The two groups of archosaurs, crocodilians and birds, form an extant phylogenetic bracket for understanding the reproductive behaviour of dinosaurs. This behaviour is inferred from preserved nests and eggs, and even gravid individuals1. Data indicate that many ‘avian’ traits were already present in Paraves—the clade that includes birds and their close relatives—andthat the early evolution of the modern avian form of reproduction was already well on its way2,3. Like living neornithine birds, non-avian maniraptorans had daily oviposition and asymmetrical eggs with complex shell microstructure, and were knownto protect their clutches4–6.However, like crocodilians, non-avian maniraptorans had two active oviducts (one present in living birds), relatively smaller eggs, and may not have turned their eggs in the way that living birds do1,6. Here we report on the first discovery of fossilized mature or nearly mature ovarian follicles, revealing a previously undocumented stage in dinosaur reproduction: reproductively active females near ovulation. Preserved in a specimen of the long bony-tailed Jeholornis and two enantiornithine birds from the Early Cretaceous period lacustrine Jehol Biota in northeastern China, these discoveries indicate that basal birds only had one functional ovary, but retained primitive morphologies as a result of their lower metabolic rate relative to living birds. They also indicate that basal birds reached sexual maturity before skeletal maturity, as in crocodiles and paravian dinosaurs. Differences in follicular morphology between Jeholornis and the enantiornithines are interpreted as forming an evolutionary gradient from the reproductive condition in paravian dinosaurs towards neornithine birds. Furthermore, differences between the two enantiornithines indicate that this lineage might also have evolved advanced reproductive traits in parallel to the neornithine lineage. en
dc.description.librarian hj2013 en
dc.description.librarian mn2013
dc.description.sponsorship The National Basic Research Program of China (973 Program, 2012CB821906), the National Natural Science Foundation of China (41172020) and the Chinese Academy of Sciences. en
dc.description.uri en
dc.identifier.citation Zheng, X, O'Connor, J, Huchzermeyer, F, Wang, X, Wang, Y, Wang, M & Zhou, Z 2013, 'Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour', Nature, vol. 495., pp. 507-511. en
dc.identifier.issn 0028-0836 (print)
dc.identifier.issn 1476-4687 (online)
dc.identifier.other 10.1038/nature11985
dc.language.iso en en
dc.publisher Nature Publishing Group en
dc.rights © 2013 Macmillan Publishers Limited. All rights reserved en
dc.subject Preservation en
dc.subject Ovarian follicles en
dc.subject Avian reproductive behaviour en
dc.subject.lcsh Birds -- Reproduction en
dc.title Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour en
dc.type Postprint Article en

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