Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA) - PubMed (original) (raw)

. 2009 Oct 7;276(1672):3429-37.

doi: 10.1098/rspb.2009.0812. Epub 2009 Jul 1.

Peter M Morris, Adam McMahon, Emrys Jones, Andy Gize, Joe H S Macquaker, George Wolff, Anu Thompson, Jim Marshall, Kevin G Taylor, Tyler Lyson, Simon Gaskell, Onrapak Reamtong, William I Sellers, Bart E van Dongen, Mike Buckley, Roy A Wogelius

Affiliations

Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation, North Dakota (USA)

Phillip L Manning et al. Proc Biol Sci. 2009.

Abstract

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).

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Figures

Figure 1.

Figure 1.

Dorsal surface of mid-section from the forearm of MRF-03. Detail of the fossil displaying three-dimensional aspect of skin preservation. The skin is not a typical trace fossil, but mineralized integument with depth and structure. Scale bar, 10 cm.

Figure 2.

Figure 2.

(a) Transmitted light micrograph image of skin: black/grey layer in the upper portion of the slide is skin. White box indicates area scanned in (b). (b) Skin in thin section imaged via back-scattered electron imaging (BSEI). Arrows indicate the dark organic-rich layers that bound the skin at top and bottom. Small rectangle indicates the approximate location of area detailed in (c). (c) BSEI image of the skin thin section showing structures that closely resemble cellular aggregates both in size and in morphology. Epidermal boundary between distinct tissue types (d). ESEM image taken from a non-carbon-coated cross section of skin. Image indicates laminated structure within the upper laminated portion of the skin from MRF-03.

Figure 3.

Figure 3.

Electron microprobe false colour intensity map of calcium distribution within a thin section of the skin of MRF-03 (map size: 450 µm × 365 µm). Calcite (identified by SEM and optical microscopy) has precipitated as either hollow rings or small equant crystals, approximately 20 µm in diameter. Total inferred epidermal thickness here is 2.5–3.5 mm.

Figure 4.

Figure 4.

Stingray FTIR (transmission mode) map (a) of the intensity of absorption at 1654 cm−1 corresponding to a probable distribution of amide (I) groups on sediment grains sampled from the sheath covering the terminal ungual phalanx region of MRF-03. The corresponding spectrum (b, row, 25; column, 5) (from the point on the crosshairs in the map) suggests that both amide I and II groups are present in the mapped organic residue (corresponding peaks located at 1654 and 1522 cm−1, respectively), and thus is inferred to indicate the presence of protein or protein breakdown products. Reference spectra from reptilian (c, terminal ungual phalanx from juvenile Crocodylus porosus) and avian (d, down feather from Columba livia) beta-keratin are shown for comparison; amide I peaks are indicated with vertical dashed lines at 1630 and 1644 cm−1, respectively.

Figure 5.

Figure 5.

(a) Amino acid composition plots of four samples taken from the dinomummy and one of the sediment blanks. The skin envelope appears to contain a distinct composition, potentially containing endogenous protein. Asx, asparagine; Glx, glutamic acid; Ser, serine;

l

-Thr,

l

-threonine; Gly, glycine;

l

-Arg,

l

-arginine; Ala, alanine; Val, valine. Cross, sediment blank; small open circle, small fragment of keratinous sheath; small filled circle, large fragment of keratinous sheath; large filled square, skin isolated from arm; diamond, skin envelope from base of tail. (b) Glycine/alanine ratios in samples taken from various locations within the specimen. The skin in the tail region had the highest glycine/alanine ratios, similar to those expected in structural proteins such as collagens and keratins, and was therefore selected as the best candidate for proteomics analysis.

Figure 6.

Figure 6.

Partial Py-GCMS total ion current chromatograms of (a) the skin envelope and (b) the surrounding sediment associated with the skin envelope. The insets show the m/z 57 mass chromatograms revealing the distribution of _n_-alkane moieties with numbers indicating the carbon chain length. -, n_-alkane; *, n_-alkene; o, aldehyde; c, contaminant; si, silicon-containing compounds; bn, benzonitrile; bt, benzothiophene; df, dibenzofuran; p, phenanthrene; ?, unknown moiety; b_x, benzene derivative; n_x, napthalene derivative, where x represents the number of carbon atoms in the alkyl group.

Figure 7.

Figure 7.

Stingray FTIR (reflection mode) images (left) and spectra (right) of a sample taken from a section of ossified epaxial tendon from MRF-03. This shows a cross section through three Haversian canals. (a) Map of the intensity of adsorption at 1170 cm−1—crosshairs on the map (left) show from where the spectrum (right) has been selected. The Haversian canals within the apatite are clear. (b) An approximately 20 µm thick carbon dioxide-rich layer on the apatite is evident, again crosshairs on the map show where the spectrum (right) originates from. (c) Absorption bands at approximately 1770 cm−1 noted at several places on the sample mapping them showed clear structural control and suggests that organic material may persist associated with the canals.

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