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Proc Natl Acad Sci U S A. 2018 Oct 16;115(42):10708-10713. doi: 10.1073/pnas.1812176115. Epub 2018 Sep 24.

A new clade of basal Early Cretaceous pygostylian birds and developmental plasticity of the avian shoulder girdle.

Author information

1
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China; wangmin@ivpp.ac.cn zhouzhonghe@ivpp.ac.cn.
2
Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Beijing 100044, China.
3
Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China.

Abstract

Early members of the clade Pygostylia (birds with a short tail ending in a compound bone termed "pygostyle") are critical for understanding how the modern avian bauplan evolved from long-tailed basal birds like Archaeopteryx However, the currently limited known diversity of early branching pygostylians obscures our understanding of this major transition in avian evolution. Here, we describe a basal pygostylian, Jinguofortis perplexus gen. et sp. nov., from the Early Cretaceous of China that adds important information about early members of the short-tailed bird group. Phylogenetic analysis recovers a clade (Jinguofortisidae fam. nov.) uniting Jinguofortis and the enigmatic basal avian taxon Chongmingia that represents the second earliest diverging group of the Pygostylia. Jinguofortisids preserve a mosaic combination of plesiomorphic nonavian theropod features such as a fused scapulocoracoid (a major component of the flight apparatus) and more derived flight-related morphologies including the earliest evidence of reduction in manual digits among birds. The presence of a fused scapulocoracoid in adult individuals independently evolved in Jinguofortisidae and Confuciusornithiformes may relate to an accelerated osteogenesis during chondrogenesis and likely formed through the heterochronic process of peramorphosis by which these basal taxa retain the scapulocoracoid of the nonavian theropod ancestors with the addition of flight-related modifications. With wings having a low aspect ratio and wing loading, Jinguofortis may have been adapted particularly to dense forest environments. The discovery of Jinguofortis increases the known ecomorphological diversity of basal pygostylians and highlights the importance of developmental plasticity for understanding mosaic evolution in early birds.

KEYWORDS:

Mesozoic; bird; development; phylogeny; plasticity

PMID:
30249638
PMCID:
PMC6196491
DOI:
10.1073/pnas.1812176115
[Indexed for MEDLINE]
Free PMC Article

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