Forerunners of Mammals: Radiation, Histology, Biology

Forerunners of Mammals: Radiation, Histology, Biology

Forerunners of Mammals: Radiation, Histology, Biology

Forerunners of Mammals: Radiation, Histology, Biology


About 320 million years ago a group of reptiles known as the synapsids emerged and forever changed Earth's ecological landscapes. This book discusses the origin and radiation of the synapsids from their sail-backed pelycosaur ancestor to their diverse descendants, the therapsids or mammal-like reptiles, that eventually gave rise to mammals. It further showcases the remarkable evolutionary history of the synapsids in the Karoo Basin of South Africa and the environments that existed at the time. By highlighting studies of synapsid bone microstructure, it offers a unique perspective of how such studies are utilized to reconstruct various aspects of biology, such as growth dynamics, biomechanical function, and the attainment of sexual and skeletal maturity. A series of chapters outline the radiation and phylogenetic relationships of major synapsid lineages and provide direct insight into how bone histological analyses have led to an appreciation of these enigmatic animals as once-living creatures. The penultimate chapter examines the early radiation of mammals from their nonmammalian cynodont ancestors, and the book concludes by engaging the intriguing question of when and where endothermy evolved among the therapsids.


This book brings together a group that has over many years researched various aspects of the evolution and paleobiology of the synapsids. Many of us have collaborated in our research endeavors, and all of us have at some stage shared information and had many hearty discussions about the biology of our distant relatives.

The book comprises eleven chapters. the first two chapters provide an introduction to the predecessors of mammals and their relatives, and an assessment of the ancient world in which they radiated. the opening chapter sets the scene, providing a guide of “who” the synapsids were and how they are related to one another. in this chapter, Tom Kemp provides an up to date assessment of the radiation of the synapsids from their earliest pelycosaur members, to the diverse nonmammalian therapsids, and later to the increasingly more mammal-like cynodonts. All this is done from a global perspective.

The second chapter of this book deals more specifically with the Karoo Basin of South Africa and documents an unparalleled track record of the evolution and radiation of the therapsids. Here, Karoo paleontologists, Roger Smith and Bruce Rubidge, together with a recent PhD graduate Merrill van der Walt, provide a unique perspective of therapsid biodiversity and paleoenvironmental analysis of the Karoo Basin of South Africa. For the first time, faunal turnover in the Karoo Basin is provided through a lens of absolute numbers of genera and have permitted detailed trophic level analyses for each of the biozones.

The third chapter by yours truly sets the scene for the bone microstructure chapters that follow. the first part of this chapter takes the form of an atlas of bone microstructure that will enable a novice to identify particular types of bone tissues in synapsids. the second part examines the biological implications of particular types of bone microstructures and how these can be utilized to deduce various aspects of the biology of extinct animals.

The next seven chapters focus on particular synapsid lineages. Each of these chapters is structured to provide a phylogenetic and paleobiological context before delving into the bone microstructure of that particular group. the first in this series of chapters (chapter 4) predictably deals with the earliest members of the Synapsida, the pelycosaurs. Here, Adam Huttenlocker and Elizabeth Rega present an overview of the bone microstructure of pelycosaurian-grade synapsids from both “normal” and pathological skeletal elements.

The fifth chapter is by Sanghamitra Ray, my former postdoctoral fellow, Jennifer Botha-Brink, my former PhD student, and me. Here we . . .

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