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Biomarkers and their application to the study of pigments in the fossil record

Jones, Holly Elisabeth

[Thesis]. Manchester, UK: The University of Manchester; 2013.

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Abstract

The idea of studying the colour of organisms in the fossil record has for a long timeseemed nothing more than the far flung dreams of a few idealistic palaeontologists.The last 5 years however have brought sweeping advances in this area, such that theidea is no longer hypothetical but an actual possibilty. Recent studies on the preserva-tion of fossilised pigment containing organelles, melanosomes, have hailed a new eraof palaeontological study and reconstruction. In this work geochemical techniques areapplied to study such structures in fossil feathers and an amphibian, to determine thenecessary level of confidence that these structures are not bacterial, discuss the relativeadvantages and disadvantages of the techniques used in the study of fossil melanin, andextend the study of fossil colour to other pigments in fossil algae. Fourier transforminfrared spectroscopy (FTIR) data is shown to provide some of the most consistentevidence of the presence of melanin, however it does not enable us to adequately dis-tinguish between the two major types, eu- and pheomelanin. Determining the presenceof bacteria in fossil stromatolites is shown to be most effective by using tetra-methylammonium hydroxide assisted pyrolysis gas chromatography mass spectrometry (Py-GCMS) to look for the distribution pattern of fatty acid methyl esters. Such analysisshows that samples identified as bacterial have identical patterns that differ signifi-cantly from those of fossil plants and animals. Such a biomarker is shown to be morereliable than hopanes, further commonly used bacterial biomarkers. The combination of FTIR and Py-GCMS suggest the presence of the red algal pigment phycoerythrin inthe Jurassic fossil Solenopora jurassica, strengthening its identification as a calcareousalga.

Layman's Abstract

The study of pigments in for fossil record as being used to determine the colour of long extinct animals is a burgeoning field of palaeontology. In this thesis we apply geochemical techniques to their study to tease out what we can tell about their chemistry and what that can tell us about the fossils they come from. We use chemistry to determine the presence of the dark pigment eumelanin in the feathers of the early Cretaceous bird Gansus yumenensis to show that its feathers were darkly coloured. We study a similar pigment in a fossil tadpole that shows signs of the related molecule pheomelanin but cannot conclusively demonstrate its presence. We also study pigments in a fossil alga and show evidence that it contains the red algal pigment phycoerythrin, the first time this has been shown. The presence of this pigment also supports the identification of this specimen as an alga. The final part of the thesis is a study into the organic material preserved in bacterial mat fossils of different ages, showing that there is a unique chemical signature that can be used to distinguish bacteria in the fossil record. This helps significantly in teasing apart which geochemical signals have been left by original pigments in soft tissues like skin and feathers, and which come from bacteria.