To determine the structural and chemical composition of the soft tissues Lindgren collected and see if the fossil sea turtle did have a dark colored shell, the researchers subjected the sample to a selection of high - resolution analytical techniques, including field emission
gun scanning electron microscopy (FEG - SEM), transmission electron microscopy (TEM), in situ immunohistochemistry, time - of - flight secondary ion mass spectrometry (ToF - SIMS), and infrared (IR) microspectroscopy.