Pterosaurs (flying prehistoric reptiles) and dinosaurs (also reptiles) share a common reptilian ancestor that lived some 240 million years ago, but the two groups then followed different evolutionary paths.
Dinosaurs are characterised by distinctive features of the skeleton, including a window-like opening in the pelvis where the thigh bone connects. Pterosaurs don’t have this joint, and they have their own unique features such as extra-long fourth fingers that support their wings. Pterosaurs are no more dinosaurs than we are chimpanzees.
Steve is a professor and palaeontologist at the University of Edinburgh and the author of the book The Rise And Reign Of The Mammals (£20, Picador), a 325-million-year odyssey of mammalian evolution and the people who study mammal fossils.