Argentine palaeontologist, Prof. Rosendo Pascual, in his laboratory at the National University of La Plata. Professor Pascual is the discoverer of a 63 million-year-old tooth of a Platypus/Ornitho- rhynchidae ancestor in South America. Here, he is seen examining the fossil tooth microscopically. Beside the microscope is a skull of the present- day Platypus, and next to it a cast of the proposed ancestor from which this fossil tooth came. The discovery, made in 1991, sheds light on monotremes, the most primitive of living mammals. Living specimens are only known from Australia and New Guinea, but this tooth gives evidence of a South American ancestor.