Tullimonstrum gregarium, better known as the \u2018Tully Monster\u2019 is a problematic fossil from the Late Carboniferous Mazon Creek lagerst\xe4tte, Illinois, USA. The identity of this fossil has been the subject of much debate, due to its peculiar form. Several competing hypotheses have placed it within the arthropods, fish, worms or even molluscs.\n\xa0\nJoining us in this interview is Dr Victoria McCoy whose work at Yale University (recently published in Nature) was able to demonstrate that the Tully Monster belonged to a different group entirely.