Integumentary structure and composition in an exceptionally well-preserved hadrosaur (Dinosauria: Ornithischia)
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Abstract
Preserved labile tissues (e.g. skin, muscle) in the fossil record of terrestrial vertebrates are increasingly becoming recognized as an important source of biological and taphonomic information. Here, we combine a variety of synchrotron radiation techniques with scanning electron and optical microscopes to elucidate the structure of 72 million-year-old squamous (scaly) skin associated with a hadrosaurid dinosaur from the Late Cretaceous of Alberta, Canada. Scanning electron and optical microscopy independently reveal that the three-dimensionally preserved scales are associated with a band of carbon-rich layers up to a total thickness of 75 μm. Compositionally, this band deviates from that of the surrounding matrix; Fourier-transform infrared spectroscopy and soft X-ray spectromicroscopy analyses indicate the presence of carboxylic compounds. The regions corresponding to the integumentary layers are distinctively enriched in iron compared to the associated sedimentary matrix and seem associated to kaolinite. These carbonyl-rich layers are apparently composed of subcircular bodies resembling preserved cell structures. Each of these structures is encapsulated by calcite/vaterite, with iron predominantly concentrated at its center. The presence of iron, calcite/vaterite and kaolinite might have played important roles in the preservation of the layered structures.
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2019. Integumentary structure and composition in an exceptionally well-preserved hadrosaur (Dinosauria: Ornithischia) PeerJ Preprints 7:e27698v1 https://doi.org/10.7287/peerj.preprints.27698v1note This preprint is not peer-reviewed. You may wish to reference the subsequent peer-reviewed version of this article.
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Supplemental Information
Integumentary structure and composition in an exceptionally well-preserved hadrosaur (Dinosauria: Ornithischia): Supplemental Material
Extra information and data, including chemical spectroscopic data and maps are included in this supplemental material
XRF distribution for iron, calcium, copper and manganese
XRF distribution for iron, calcium, copper and manganese. Each pixel measures 25 micron-square; the entire mapped area measures 89.9 micron x 330 micron. Warmer colours correspond to higher concentrations for each element. Maps were plotted using PyMCA (Sole,2007). The concentration of iron, and to a lesser extent, copper, is higher in the region preserving the integument (region between the dashed lines) than to the sediment surrounding it.
SEM spectrum
SEM spectrum from point 6 as indicated in Fig. 2c.
SEM spectrum
SEM spectrum from point 5 as indicated in Fig. 2c.
SEM spectrum
SEM spectrum from point 4 as indicated in Fig. 2c.
SEM spectrum
SEM spectrum from point 3 as indicated on Fig. 2c.
SEM spectrum
SEM spectrum from point 1 as indicated in Fig. 2c.
MidIR spectra
Complete set of spectra collected at the MidIR beamline endstation corresponding to the points indicated in Fig. 7.
Spectra collected from the light powder sample
Set of spectra collected from the light powder sample. The absence of any remarkable peaks in the "organic" region of the spectrum, situated between 1500 - 1800 cm-1, is in clear contrast relative to the same region identified in the spectral collection for the dark powder shown in Fig. S7.
Aluminum component maps
Aluminum component maps derived from the linear regression fitting of an Al K-edge image sequence using reference spectra. (a) Comparison of Al 4-fold coordinated and Al 4, 6-fold coordinated spectra derived by threshold masking of the component maps to the muscovite (4, 6-fold coordinated), gibbsite (6-fold coordinated Al) and AlPO4 (4-fold coordinated Al) reference spectra. Component maps (b-e). (b) 4-fold coordinated Al, (c) 4, 6-fold coordinated Al and (d) slow varying featureless signal (FS). (e) Color composite of the component maps (4-fold coordinated Al = red, featureless signal = green and 4, 6-fold coordinated Al = blue).
Magnesium component map
Magnesium component map derived from the linear regression fitting of an Mg K-edge image sequence using a spectrum taken from the image sequence. (a) Mg spectrum from the crystals (sediment). Component maps: (b) Mg and, (c) slow varying featureless signal (FS). Color composite of the component maps (Mg = red; featureless signal = blue).
Silicon component maps
Silicon component maps derived from the linear regression fitting of an Si K-edge image sequence using spectra taken from the image sequence. (a) Si spectra (Si species 1 and Si species 2) derived by threshold masking of the respective component maps. (b) Overlay of the Si spectra. Orange box shows the area expanded from (a). Component maps: (c) Si Species 1, (d) Si Species 2 and (e) slow varying featureless signal (FS). (f) Color composite of the component maps (Si species 1 = red, featureless signal = green and Si species 2 = blue).
Additional Information
Competing Interests
James J. Dynes is employed by Canadian Light Source Inc.
Author Contributions
Mauricio Barbi conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Phil R. Bell conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Federico Fanti conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, authored or reviewed drafts of the paper, approved the final draft.
James J. Dynes conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Anezka Kolaceke conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Josef Buttigieg conceived and designed the experiments, performed the experiments, contributed reagents/materials/analysis tools, prepared figures and/or tables, authored or reviewed drafts of the paper, approved the final draft.
Philip J. Currie authored or reviewed drafts of the paper, approved the final draft.
Field Study Permissions
The following information was supplied relating to field study approvals (i.e., approving body and any reference numbers):
Palaeontological Collecting Permits issued by the Historical Resources Division (through the Royal Tyrrell Museum of Palaeontology) of the Government of Alberta
Data Deposition
The following information was supplied regarding data availability:
All data are presented as spectral histograms. Chemical maps in this work are qualitative rather than quantitative, with no importance given to absolute values. In fact, the nature of this work is fundamentally qualitative.
Funding
This work was supported by the Australian Research Council DECRA award (project ID: DE170101325) and by the Faculty of Sciences, University of Regina, Canada. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
