Fossils, at the best of times, are difficult to interpret. Palaeontologists attempt to reconstruct organisms from what little remains are left. This can be relatively simple for groups that we are familiar with today; you can easily make comparisons between a fossil lobster and a living one. But how do you interpret a fossil that has no modern counterpart and is not clearly related to any other organism?  We speak to Dr Jakob Vinther of the University of Bristol about his experience of interpreting some of the oldest and most cryptic specimens in the fossil record.  We look at molluscs, worms, worm-like molluscs and mollusc-like worms.