25th International Meeting on Organic Geochemistry IMOG 2011

O-41
Multi technique approach resolves soft-tissue preservation in 50
million year old reptile skin
Bart van Dongen 1,2 , Phill Manning 1,2,6 , Nick Edwards 1,2 , Holly Barden 1,2 , Peter Larson 3 ,
Uwe Bergmann 4 , William Sellers 5 , Roy Wogelius 1,2
1 University of Manchester, School of Earth, Atmospheric, and Environmental Sciences, Manchester, United
Kingdom, 2 University of Manchester, Williamson Research Centre for Molecular Environmental Science,
Manchester, United Kingdom, 3 Black Hills Institute of Geological Research, Inc., Hill City, United States of
America, 4 SLAC National Accelerator Laboratory, Linac Coherent Light Source, Menlo Park, United States
of America, 5 University of Manchester, Faculty of Life Sciences, Manchester, United Kingdom, 6 University of
Pennsylvania, Department of Earth and Environmental Sciences, Philadelphia, United States of America
(corresponding author:Bart.vandongen@manchester.ac.uk)
Recent palaeontological research suggests that
soft-tissue may be preserved during fossilization. A
recent study of a well-preserved Upper Cretaceous
dinosaur (specimen MRF-03) unequivocally showed
differences between the organic compounds present
within the fossilized skin envelope and the enclosing
sedimentary matrix [1], suggesting preservation of
residue from endogenous organic compounds, e.g. β
keratin, within soft tissue. Unfortunately, mapping of
the β keratin products in the skin was not possible
due to the friable nature of the available samples.
However, it suggested that using a combination of
modern analytical techniques, including infra-red
mapping of organic functional groups, and more
suitable specimens may provide new constraints on
interpreting fossil preservation without requiring
destructive sampling. Therefore, a well-preserved
fossilized reptile skin (Squamata: Reptilia tent; Fig.
1A) from the Green River Formation (Utah, USA; ~50
million year old) was analysed using FTIR mapping,
Py-GC/MS and Synchrotron Rapid Scanning X-Ray
Fluorescence (SRS-XRF).
FTIR mapping of organic functional units (Fig. 1D)
show a spatial distribution of endogenous organic
components, e.g amide and sulfur compounds,
comparable to the structure of extant tissue indicating
that these are most likely derived from the original β
keratin present in the skin. This is further confirmed
by absence of the intense amide or thiol absorption
bands in fossil leaf and other non-skin derived organic
matter from the same geological formation.
Maps/spectra from the fossil are also directly
comparable to extant reptile skin. Py-GC/MS analyses
yielded diagnostic n-alkane/alkene patterns with
comparable distributions for fossil plant material and
the sedimentary matrix, suggesting that the later
contains leaf derived organics. In contrast, the
distribution pattern of the fossil skin is completely
different, suggesting that there is minimal transfer of
organics from the matrix to the skin, confirming that
the compounds mapped by FTIR are original to the
skin. Furthermore, the Py-GC/MS results also
confirmed that the organic signal identified is most
likely not of aerobic microbial origin. Elemental
mapping using SRS-XRF further showed that the
presence of both organic sulfur (Fig. 1B) and trace
metals are almost exclusively observed in the skin,
with the later probably due to chelation by melanin.
Their distribution patterns correlate well with the
functional groups mapped by FTIR.
Taken together, all the analyses performed in this
study strongly suggest that the fossilized reptile skin
is not a simple impression, mineralized replacement,
or an amorphous organic carbon film, but contains a
partial remnant of the living organism‘s original
organics, in this case derived from proteinaceous
skin. In addition, it shows that valuable information
can be obtained from rare specimens where
destructive sampling is not possible.
Fig.1. (A) photograph, (B) organic sulfur distribution
map, (C) reflected light map and (D) FTIR absorption
map at 1653cm -1 [box in Fig. 1A] of fossilised skin.
References
[1] Manning, P.L. et al. Proc Royal Soc. B 276, 3429
3437 (2009)
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