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

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  • 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 date: 2019-04-15

  Online published: 2020-01-20

Copyright

, 2020, Copyright reserved © 2020.

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.

Cite this article

Jingmai K. O’CONNOR, Amanda FALK, WANG Min, ZHENG Xiao-Ting . First report of immature feathers in juvenile enantiornithines from the Early Cretaceous Jehol avifauna[J]. Vertebrata Palasiatica, 2020 , 58(1) : 24 -44 . DOI: 10.19615/j.cnki.1000-3118.190823

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