Recent work with lizards has shaken the long-standing assumption in biology that only mammals have placentas. Daniel G Blackburn of Trinity College in Hartford, Connecticut, and Alexander F Flemming of Stellenbosch University have found that a lizard – the skink Trachylepsis ivensii – is an exception. While many reptiles give birth to live young, they do not have embryos that implant themselves into the mother and connect to her circulatory system via a true placenta. The discovery of placentas in two distinct groups of animals may help biologists to figure out how they evolved.