Vertebrate palaeontology is always in the news: fossil hunters argue about which was the biggest dinosaur of all, or the biggest flesh-eater; someone claims to have found dinosaur blood cells, and even to have extracted dinosaur DNA; an ancient fossil bird is announced that adds 100 million years to their history; ever-older specimens of human beings are unearthed in Africa. When I wrote this book, in 1989, I felt that there was a need for an up-to-date account of what is known about the history of vertebrates, but also for a summary of the latest of these exciting discoveries. The first edition was published in 1990. When I was asked to prepare a second edition, I set aside 2 months to make a few changes to the text, and add some new illustrations. I thought the task of revision would be fairly minor. Now, after 5 months of intensive work, very little of the original edition remains untouched. I was amazed at how much had happened in my science in the course of 7 years, and how the new work has substantially changed our views, par- ticularly in disentangling the relationships of vertebrates. In updating the book, I made no deliberate attempt to include 1995 and 1996 references, and yet the sheer numbers show how many major new discoveries there have been. This makes me very nervous about the future shelf-life of the book if this rate of discovery and exciting new research work continues.