The Tully ‘monster’ is a prehistoric animal that –at 15 cm – isn’t exactly monstrous, however its strange structure made it difficult to classify as a vertebrate or invertebrate. The 300-million-year-old ‘monster’ was discovered by amateur fossil hunter, Francis Tully, at a site known as Mazon Creek Lagerstätte in the U.S. state of Illinois. This characteristic is not known in …
