Fossil pigments and pigment organelles - colouration in deep time

Sammanfattning: Pigmentation is important in all animals and plants, e.g., for protection against radiation, for signalling and as camouflage. The fossil record contains both colourful bird feathers and insect cuticles. The question is if original pigments and colours can be spared from diagenetic alteration through millions of years. This study uses SEM (scanning electron microscopy) and EDX (energy dispersive X-ray spectrometry) to examine the eyes of a fossil insect and a fossil feather, both from the Eocene Fur Formation, Denmark and two fossil feathers from the Eocene Green River Formation, USA. The EDX analysis showed elevated carbon intensities in the dark peripheral of the ommatidia and elevated calcium intensities towards the centre of each ommatidium. Elevated carbon and sulphur intensities were observed in all feathers relative to the surrounding matrix. The carbon in all four specimens is interpreted as originating from organic matter present in the fossils. The calcium in the insect eye is interpreted as the preserved crystalline cones of the ommatidia. It is possible that original pigments and pigments organelles are preserved; however this cannot be confirmed by the methods used in this study.