Richard Fortey has devoted his long and prolific research career at the Natural History Museum in London to the study of fossils, especially the long-extinct marine arthropods called trilobites.  In an earlier episode of Geology Bites, he talked about measuring time with trilobites. In this episode, he describes how it was the fossils in the geological record that gave us the first markers along the runway of deep time, providing the structure and language within which our modern conception of deep time emerged.