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Vertebrata Palasiatica ›› 2020, Vol. 58 ›› Issue (1): 24-44.DOI: 10.19615/j.cnki.1000-3118.190823

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First report of immature feathers in juvenile enantiornithines from the Early Cretaceous Jehol avifauna

Jingmai K. O’CONNOR1,2,*(), Amanda FALK3, WANG Min1,2, ZHENG Xiao-Ting4,5   

  1. 1 Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences Beijing 100044, China
    2 CAS Center for Excellence in Life and Paleoenvironment Beijing 100044, China
    3 Centre College 600 W. Walnut St. Danville, Kentucky 40422, USA
    4 Institute of Geology and Paleontology, Linyi University Linyi, Shandong 276000, China
    5 Shandong Tianyu Museum of Nature Pingyi, Shandong 273300, China
  • Received:2019-04-15 Online:2020-01-20 Published:2020-01-20
  • Contact: *jingmai@ivpp.ac.cn;

未成熟羽毛在早白垩世热河鸟类生物群幼年反鸟类中的首次报道

邹晶梅1,2,*(), 福雅曼3, 王敏1,2, 郑晓廷4,5   

  1. 1 中国科学院古脊椎动物与古人类研究所,中国科学院脊椎动物演化与人类起源重点实验室 北京 100044
    2 中国科学院生物演化与环境卓越创新中心 北京 100044
    3 美国森特学院生物学系 肯塔基州丹维尔 40422
    4 临沂大学地质与古生物研究所 山东临沂 276005
    5 山东省天宇自然博物馆 山东平邑 273300
  • 基金资助:
    国家自然科学基金资助(41688103);国家自然科学基金资助(41372014)

Abstract:

Molting—the process replacing one plumage with another—is a critically important biological function in Aves. This process annually replaces the feather coat, damaged by normal wear and tear, produces ontogenetic changes in feathering, and produces alternate breeding plumages associated with reproductive activity in adults. Immature, growing feathers are encased in a keratinous sheath, giving them a narrow, tubular, and featureless appearance. The complete loss of the sheath indicates the feather is mature. Despite the wealth of integumentary data published from the Jehol Biota, immature feathers have never been definitively reported, although they may potentially be preserved in a juvenile specimen of the non-avian oviraptorosaur theropod dinosaur Similicaudipteryx from the 120 Ma Jiufotang Formation. A developing feather has been reported in a 99 Ma enantiornithine neonate preserved in Burmese amber, in which three-dimensional preservation makes interpretations of integumentary structures more straightforward. Here we report on probable immature feathers in four juvenile enantiornithines (Aves: Ornithothoraces) from the Jehol Group. As observed in developing feathers in extant birds, the purported immature fossil feathers appear proximally narrow and featureless with barbs protruding only distally. Based on our observations, we suggest that similar-appearing feather structures preserved on the manus and tibiotarsus in the holotype of the enantiornithine Cruralispennia multidonta may alternatively be interpreted as immature feathers. The presence of immature feathers in combination with sexually dimorphic ornamental feathers in juvenile enantiornithines suggests the complex molting patterns of Neornithes, in which such ornaments only appear after several years (following several molts) when reproductive activity is achieved, are limited to a subset of crownward avians.

Key words: Mesozoic, Jehol Biota, Aves, pin feather, plumage, molt

摘要:

换羽——将一种羽毛替换成另一种的过程——对鸟类具有非常重要的生物学作用。这一过程能够每年将受损的羽毛替换掉,产生与个体发育相关的羽毛类型,或产生处在繁殖活跃期成年个体所具有的覆羽类型。处于萌发阶段的未成熟羽毛被角质鞘包裹,外形呈狭窄管状,没有明显特征。角质鞘完全脱落标志着羽毛的成熟。虽然热河生物群发现了大量与皮肤衍生物相关的化石,但是确切无疑的未成熟羽毛还未有报道,尽管九佛堂组(120 Ma)发现的一件窃蛋龙类——似尾羽龙,保存了疑似未成熟的羽毛。一件缅甸琥珀(9 Ma)中的反鸟幼崽保存了处于萌发阶段的羽毛,由于是三维保存,对外皮结构的解读更为直观。描述了发现于九佛堂组的4件反鸟类幼年个体上保存的疑似未成熟羽毛。与现生鸟类相似,上述疑似未成熟羽毛的近端窄,外形没有明显结构,仅在末端显示出分叉的羽支。认为此前报道的反鸟类多齿胫羽鸟(Cruralispennia multidonta)掌部和胫跗骨上的相似类型的羽毛可能也是未成熟羽毛。未成熟羽毛和与性双型相关的装饰性羽毛在反鸟类幼年个体上的同时出现,可能说明新鸟类具有的复杂的换羽模式——与性双型相关的装饰性羽毛在个体达到性成熟若干年后(经历了若干次换羽后)才会出现,并且只在更接近鸟类冠群的一些类群中出现。

关键词: 中生代, 热河生物群, 鸟类, 鞘羽, 羽毛, 换羽

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