Book Review: Laurin, M. The Advent of PhyloCode: The Continuing Evolution of Biological Nomenclature; CRC Press: Boca Raton, FL, USA; Abingdon, UK, 2024; ISBN: 978-0-367-55288-6 (hbk), 978-0-367-55210-7 (pbk), 978-1-003-09282-7 (ebk)

Birds are dinosaurs! Elementary school children will eagerly share this exciting bit of news with us these days. But do they know why? And why would no one have taught them this in school 80+ years ago? Class Aves (extant) and Class Dinosauria (extinct), in Subphylum Vertebrata in Phylum Chordata, were not two “separate and equal” entities as their common rank would suggest—one evolved from within the other. Explicitly acknowledging the role that the process of descent from a common ancestor plays in our practice of naming groups of organisms requires a re-thinking of how and why we engage in biological nomenclature. The Advent of PhyloCode addresses the intriguing history of this major transformation in our perspective and presents an argument for why it matters that we understand the distinction.

Although “a rose by any other name would smell as sweet”, as Shakespeare penned, the particular names that we establish and use are important. We name our children, our pets, and sometimes even our cars or houses, and we do this to communicate with one another more clearly and precisely about those individuals or entities. Groups of individual organisms, or named taxa in biological nomenclature, can indicate the hierarchical nature of these individuals in groups, and groups clustered in other, more inclusive, groups—or they can indicate which groups are related to others through common ancestry. The system of rank-based nomenclature commonly in use was developed by Carl Linnaeus in the 1730s, based on a hierarchy of perceived similarities and differences among organisms, primarily in morphology and development. From an evolutionary perspective, limitations in information retrieval from the Linnean system of classification have led to the development of a new code of phylogenetic nomenclature, the PhyloCode, in which names are delimited in a way to impart information about evolutionary relationships.

The subtitle—the continuing evolution of biological nomenclature—encapsulates well the content of this book and the development of the PhyloCode. The book is clearly written, thoughtful, quite dense in content but still easily readable, and packed with information that is not usually combined into a single volume. Michel Laurin is a vertebrate paleontologist at the Centre National de la Recherche Scientifique in France and has a first-hand appreciation for considering the importance of the extinction of groups of organisms as well as their origination. This dynamic perspective on evolution over long periods of “deep” geological time is helpful in understanding and explaining the purpose and value of a transition from a rank-based nomenclature to a phylogenetic nomenclature.

The book is divided into seven chapters, each with a different focus but with a temporal continuity in topics that leads readers through the history and development of rank-based nomenclature over the past 300+ years. In addition, a very useful glossary of terms is provided at the end of the book. Chapter 1 begins with a discussion of a variety of preliterate classifications, proceeds to Aristotle’s hierarchical but rank-free concept of classifying organisms, then to Linnaeus and his structure of absolute categories and binomial nomenclature, and ends with Darwin, Wallace, and the representation of evolutionary relationships in branching diagrams (“trees”). Chapter 2 discusses current rank-based codes of nomenclature and the concept of types. Chapter 3 moves to the more comprehensive understanding of modern phylogenetics and the delimitation of taxa, with examples from extant and extinct vertebrates, before reaching the conclusion that “ranks must go”. Chapter 4 introduces the principles of phylogenetic nomenclature and the development of the PhyloCode as a formal set of rules governing the naming of clades as taxa. The International Society for Phylogenetic Nomenclature was established in 2004 to communicate more broadly the nature and practice of phylogenetic nomenclature, and to encourage and facilitate its further development and utilization by evolutionary systematists and taxonomists. Chapter 5 compares this methodology to systems of nomenclature pertaining to time and space (stratigraphy and geography). Chapter 6 discusses several controversies that have arisen in the context of the PhyloCode, including possible instability of established rank-based names and the relationship of species names to clade names, among others. Finally, Chapter 7 ends with the statement that phylogenetic nomenclature is the logical outcome of progress in evolutionary biology, that its advent will be beneficial for evolutionary biology and that biological nomenclature necessarily develops through innovation and change.

Science itself is driven by innovation and curiosity. The Advent of PhyloCode provides a very useful and informative guide to the history and principles of phylogenetic nomenclature. I highly recommend this book to anyone deeply interested in the history of biology, nomenclature, and phylogenetics and its relationship to evolution, taxonomy, species concepts, and our changing perceptions of relationships among organisms. Lastly, this book is especially handy to be able to explain to anyone why birds are dinosaurs.