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 buzzard 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 was shown in the fossil by elastic backscattering (EBS) and particle-induced X-ray emission (PIXE). 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 (13C CP-MAS NMR) and pyrolysis- gas chromatography-mass spectrometry in the presence of TMAH (TMAH-Py-GC-MS). Results show that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The latter and the embedding sediment exhibit a highly aliphatic character. However, substantial differences could be evidenced between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. The preservation of the fossil feathers, primarily expressed by the preservation of their morphology, seems to be associated with in situ polymerization of endogenous lipids. Sulphur probably played a role in the fossil preservation although no natural sulphurization took place.
Supplementary material for the main manuscript
Funding provided by: Irish Research Council Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100002081 Award Number: GOIPD/2018/768