The mapping and differentiation of biological and environmental elemental signatures in the fossil remains of a 50 million year old bird

Abstract

The preservation of fossils reflects the interplay of inorganic and organic chemical processes, which should be clearly differentiated to make interpretations about the biology of extinct organisms. A new coliiformes bird (mouse bird) from the $50 million year old Green River Formation (Wyoming, USA) has here been analysed using synchrotron X-ray fluorescence and environmental scanning electron microscopy with an attached X-ray energy dispersive system (ESEM-EDS). The concentration and distribution of 16 elements (Si, P, S, Cl, K, Ca, Ti, Mg, Fe, Ni, Cu, Zn, As, Br, Ba, Hg) has been mapped for individual points on the sample. S, Cu and Zn map distinctly within visibly preserved feathers and X-ray Absorption Spectroscopy (XAS) shows that S and Cu within the feathers are organically bound in a similar manner to modern feathers. The morphological preservation of the feathers, on both macro-and microscopic scales, is variable throughout the fossil and the differences in the lateral microfacies have resulted in a morphological preservation gradient. This study clearly differentiates endogenous organic remains from those representing exogenous overprinted geochemical precipitates and illustrates the chemical complexity of the overall taphonomic process.

Interpreting melanin-based coloration through deep time: a critical review

“…To complicate matters further, impressions indistinguishable from those attributed to melanosomes are occasionally found also in clay minerals, on silica crystals, and other sedimentary grains associated with, but clearly distinct from, the fossilized tissue structures (e.g. [9,12,65]). …”

“…[14,63]) or lacking in specificity and/or relevant comparative material to rule out alternative hypotheses (e.g. [55,64,65]). Most critically, many alleged melanosomes occur only as imprints ('mouldic melanosomes' [53]), a preservation mode that implies preferential degradation of the bodies relative to the surrounding substrate [12].…”

New occurrences of fossilized feathers: systematics, taphonomy, and paleoecology of the Santana Formation of the Araripe Basin (Cretaceous), NE, Brazil

“…The light portions, were markedly preserved as imprintation. Those structures were previously interpreted as autolithified bacteria (Wuttke, 1983;Davis & Briggs, 1995), but subsequent studies revealed them as evidence of fossilized melanosomes (Vinther et al 2008;Zhang et al, 2010;Barden et al, 2011;Glass et al, 2012;2013;McNamara et al, 2013;Vitek et al, 2013;Barden et al, 2014;Li et al, 2014;Egerton et al, 2015;Vinther, 2015). This interpretation, enabled reconstructions of ancient color patterns of extinct animals, such as dinosaurs, birds, reptiles and fishes.…”

“…In addition, other techniques, such as Raman Spectroscopy (RAMAN), X-Ray Fluorescence (XRF), Gas Chromatography-Mass Spectrometry (GC-MS), among others, also can give information about their chemistry (Wogelius et al, 2011;Egerton et al, 2015), indicating possible taphonomic processes that occurred after the deposition (Davis & Briggs, 1995;Schweitzer et al, 2008;McNamara, 2013). Besides the study with ancient pigmentation, the application of these techniques are important, once it provides more information about these fossils.…”

Energy dispersive detector for white beam synchrotron x-ray fluorescence imaging

“…X-ray transmission imaging techniques using metal alloy analogues or simple binary alloy models have been insightful studies but do not provide vital information on the elemental distribution in the liquid phase and cannot be used to simultaneously image many elements in the sample [1]. Conventional Synchrotron Xray Fluorescence (SXRF) can provide detailed maps of the elemental composition by raster scanning a focused Xray beam over a sample and measuring the fluorescence spectrum on a Ge or Si based detector with only a single or relatively small number of channels [2]. This can provide spatial resolution as low as 1μm but the scanning process prohibits time resolved experiments.…”