The aim of my dissertation is to assess the preservation of biomolecules within the fossilized soft tissues of vertebrates using an integrated experimental approach of microscopy (SEM, TEM, conventional microscopes), immunostaining, mass spectrometry (ToF-SIMS), and spectroscopy (FTIR) methods, with a particular emphasis on integumentary (skin) tissues of marine reptiles. Fossilized skin is second to bone in terms of the most commonly fossilized tissue in the geological record and is an incredibly versatile organ that is in constant flux with organism’s environment. As a result, this organ has evolved a variety of appendages (e.g. scales, hair, and feathers) that integrate degradation-resistant biomolecules such as keratin (a tough, waterproof skin protein) and melanin (a biochrome pigment that give animals colouration). Detection of these biopolymers in fossils would have possible implications on behavioural biology, ecology, physiology, and evolutionary history of ancient reptiles. I currently work with a Palaeogene (Eocene, 54-million-year-old) sea turtle from the Fur Formation in Denmark and a Jurassic ichthyosaur from the Posidonia Shale, Germany. Both specimens are extraordinarily preserved with skin residues, and have come from well-known lagersätten beds that previously yielded other spectacular specimens with cellular, sub-cellular, and biomolecule constituents.