A new paper, not specific to dinosaurs but relevant to some previous publications about them.
E.T. Saitta, C. Rogers, R.A. Brooker, G.D. Abbott, S. Kumar, S.S. O'Reilly, P. Donohoe, S. Dutta, R.E. Summons, and J. Vinther (2017)
Low fossilization potential of keratin protein revealed by experimental taphonomy
Palaeontology (advance online publication)
DOI: 10.1111/pala.12299
http://onlinelibrary.wiley.com/doi/10.1111/pala.12299/fullRecent 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unpublished feather and hair fossils and published fresh and fossil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.