The Deep Roots of the Mammalian Tree

Abstract

T. S. Kemp, the author of the much revered and useful Mammal-like Reptiles and the Origin of Mammals (1982), has produced a new book with the explicit aims of (1) updating the 1982 book with regard to new fossils and (2) elaborating “at a similar level the story of what happens next—the radiation of mammals after the end of the Cretaceous” (preface). The book addresses general topics and technical issues as well, dealing with the origin of mammals in the widest possible sense, that is, truly, the history of Synapsida. The readership targeted consists mostly of university students and paleontologists, but some of the broader topics will be of interest to evolutionary biologists and most scientists with a natural history background. The amateur or layperson attempting to tackle this book will face a steep learning curve, but if successfully completed much will be learned, and it will have proven the doggedness of his/her interest. The new book is graced by a clear prose, set at a fast pace, and profusely illustrated; the accomplished writing renders discussions vivid and makes progress through the lengthy and necessarily arid anatomical descriptions, if not enjoyable, at least an alleviated task. The similarities and differences between the two titles of Kemp’s books outline the substantial overlap between these works, as well as the subtle nuances in the topics covered. The 1982 book curtailed the history of Synapsida after a short chapter on Mesozoic Mammals. The new book consists of seven chapters. The first two (Introduction, and Time and Classification) are together just 11 pages long. The following five chapters form the core of the book. Chapters 3 (Evolution of the Mammal-like Reptiles) and 4 (Evolution of Mammalian Biology) are together about 120 pages long. The following three chapters—Chapter 5 (Mesozoic Mammals, 50 pages), Chapter 6 (Living and Fossil Marsupials, 25 pages) and Chapter 7 (Living and Fossil Placentals, 52 pages)—pertain to Mammalia as defined in this work (a traditional and conservative character-based definition highlighting the presence of a dentary condyle). Therefore, the book is organized along a phylogenetic axis with the exception of Chapter 4. This emphasis on phylogeny is reinforced assiduously by large and