Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird
            <i>Eoconfuciusornis</i>

Pan, Yanhong; Zheng, Wenxia; Moyer, Alison E.; O’Connor, Jingmai K.; Wang, Min; Zheng, Xiaoting; Wang, Xiaoli; Schroeter, Elena R.; Zhou, Zhonghe; Schweitzer, Mary H.

doi:10.1073/pnas.1617168113

Cited by 62 publications

(58 citation statements)

References 44 publications

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“…; Pan et al . ), should be reexamined. Furthermore, thermal experiments that report preserved morphological structures of feathers with weak and diffuse antibody signal persisting after a decade‐long exposure at 350°C (Moyer et al .…”

Section: Resultsmentioning

confidence: 99%

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Low fossilization potential of keratin protein revealed by experimental taphonomy

et al. 2017

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Recent studies have suggested the presence of keratin in fossils dating back to the Mesozoic. However, ultrastructural studies revealing exposed melanosomes in many fossil keratinous tissues suggest that keratin should rarely, if ever, be preserved. In this study, keratin's stability through diagenesis was tested using microbial decay and maturation experiments on various keratinous structures. The residues were analysed using pyrolysis‐gas chromatography‐mass spectrometry and compared to unpublished feather and hair fossils and published fresh and fossil melanin from squid ink. Results show that highly matured feathers (200–250°C/250 bars/24 h) become a volatile‐rich, thick fluid with semi‐distinct pyrolysis compounds from those observed in less degraded keratins (i.e. fresh, decayed, moderately matured, and decayed and moderately matured) suggesting hydrolysis of peptide bonds and potential degradation of free amino acids. Neither melanization nor keratin (secondary) structure (e.g. ⍺‐ vs β‐keratin) produced different pyrograms; melanin pyrolysates are largely a subset of those from proteins, and proteins have characteristic pyrolysates. Analyses of fossil fur and feather found a lack of amides, succinimide and piperazines (present even in highly matured keratin) and showed pyrolysis compounds more similar to fossil and fresh melanin than to non‐matured or matured keratin. Although the highly matured fluid was not water soluble at room temperature, it readily dissolved at elevated temperatures easily attained during diagenesis, meaning it could leach away from the fossil. Future interpretations of fossils must consider that calcium phosphate and pigments are the only components of keratinous structures known to survive fossilization in mature sediments.

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Section: Resultsmentioning

confidence: 99%

“…; Pan et al . ). These experiments indicate the preservation of tertiary protein structure, but use a method prone to false positives or statistical artefacts (Buckley et al .…”

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confidence: 97%

Low fossilization potential of keratin protein revealed by experimental taphonomy

et al. 2017

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“…; Pan et al . ), although this method remains highly controversial. By contrast, melanin (the natural pigment present in a variety of soft tissues including hair, skin and feathers) is considered to be more resistant to degradation and fossilization processes.…”

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confidence: 99%

Chemical preservation of tail feathers fromAnchiornis huxleyi, a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic, China)

Cincotta

Colaux

et al. 2020

Palaeontology

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A panel of geochemical techniques is used here to investigate the taphonomy of fossil feathers preserved in association with the skeleton of the Jurassic theropod Anchiornis huxleyi. Extant feathers were analysed in parallel to test whether the soft tissues morphologically preserved in the fossil also exhibit a high degree of chemical preservation. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicate that clays and iron oxide pseudomorphs occur in the surrounding sediment and also reveal the preservation of melanosome‐like microbodies in the fossil. Carbon gradient along a depth profile and co‐occurrence of carbon and sulphur are shown in the fossil by elastic backscattering (EBS) and particle‐induced x‐ray emission (PIXE), which are promising techniques for the elemental analysis of fossil soft tissues. The molecular composition of modern and fossil soft tissues was assessed from micro‐attenuated total reflectance fourier transform infrared spectroscopy (micro‐ATR FTIR), solid‐state 13C nuclear magnetic resonance (CP‐MAS 13C NMR) and pyrolysis gas chromatography mass spectrometry in the presence of TMAH (TMAH‐Py‐GC‐MS). Results indicate that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The fossil feathers and the embedding sediment exhibit a highly aliphatic character. However, substantial differences exist between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. Our results suggest that, despite the morphological preservation of Anchiornis feathers, original proteins, that is keratin, were probably not preserved in the 160‐myr‐old feathers.

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“…Notably, we propose that the very dense arrangement of melanosomes in the fossil feathers ( Fig. 2 B, C, and G-I, yellow arrows) does not reflect in-life distribution, but is, rather, a taphonomic response to postmortem or postburial compression (25).…”

Section: Resultsmentioning

confidence: 85%

The molecular evolution of feathers with direct evidence from fossils

Pan

Zheng

Sawyer

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Dinosaur fossils possessing integumentary appendages of various morphologies, interpreted as feathers, have greatly enhanced our understanding of the evolutionary link between birds and dinosaurs, as well as the origins of feathers and avian flight. In extant birds, the unique expression and amino acid composition of proteins in mature feathers have been shown to determine their biomechanical properties, such as hardness, resilience, and plasticity. Here, we provide molecular and ultrastructural evidence that the pennaceous feathers of the Jurassic nonavian dinosaur Anchiornis were composed of both feather β-keratins and α-keratins. This is significant, because mature feathers in extant birds are dominated by β-keratins, particularly in the barbs and barbules forming the vane. We confirm here that feathers were modified at both molecular and morphological levels to obtain the biomechanical properties for flight during the dinosaur–bird transition, and we show that the patterns and timing of adaptive change at the molecular level can be directly addressed in exceptionally preserved fossils in deep time.

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Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis

Cited by 62 publications

References 44 publications

Low fossilization potential of keratin protein revealed by experimental taphonomy

Low fossilization potential of keratin protein revealed by experimental taphonomy

Chemical preservation of tail feathers fromAnchiornis huxleyi, a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic, China)

The molecular evolution of feathers with direct evidence from fossils

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