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The field of systematics has developed remarkably over the last few decades. A multitude of new methods and contributions from diverse biological fields — including molecular genetics and developmental biology — have provided a wealth of phylogenetic hypotheses, some confirming traditional views and others contradicting them. There is now sufficient evidence to draw up a ‘tree of life’ based on fairly robust phylogenetic relationships. This book aims to apply these new phylogenies to an evolutionary interpretation of animal organ systems and body architecture. Organs do not appear suddenly during evolution: instead they are composed of far simpler structures. In some cases, it is even possible to trace particular molecules or physiological pathways as far back as pre-animal history. What emerges is a fascinating picture, showing how animals have combined ancestral and new elements in novel ways to form constantly changing responses to environmental requirements. The book starts with a general overview of animal systematics to set the framework for the discussion of organ system evolution. The chapters deal with the general organization, integument, musculature, nervous system, sensory structures, body cavities, excretory, respiratory and circulatory organs, the intestinal and reproductive system, and spermatozoa. Each organ system is presented with its function, the diversity of forms that are realized among metazoan animals, and the reconstruction of its evolution.

Patterns in Nature is a collection of eleven new essays. The work is an attempt to articulate an intellectual agenda for the study of the conceptual foundations of systematics and taxonomy in a way that connects classification with larger historical themes in the biological sciences, including morphology, experimental and observational approaches, evolution, biogeography, debates over form and function, character transformation, and biodiversity. The volume has two overarching themes. The first is to throw light on the current state of systematics by understanding the details of its history and the history of closely related disciplines and debates. The second theme is to provide enough of the details about the chronology and changes in concepts and contexts that a new generation of researchers will have a framework for taking up questions. While evolutionary systematics represents an important chapter in the recent history of biology, the rise of cladistics in the 1970s and 1980s argues for attention to Willi Hennig and his forerunners, collaborators, interlocutors, and critics. In an attempt to fill in a largely unwritten history and a lacuna in the conceptual map of modern systematics, Patterns in Nature features discussions of the work of Adolf Naef, Walter Zimmermann, Leon Croizat, Lars Brundin, and Colin Patterson, among others. This book also asks after the future of systematics, with chapters that discuss some recent and new additions to theory and practice that technology has made possible.

The understanding of arthropod phylogeny and evolution in the past three decades has undergone major changes. These have arisen from new sources of data applicable across several fields of study. Developments within ontogenetic studies not only in regard to gross patterns of embryology but also regarding a revolution in the application of development genetics continue to generate remarkable insights into crustaceomorph evolution. Phylogeny techniques of analysis and new sources of data derived from molecular sequencing have forced consideration of new hypotheses concerning the interrelationships of all the pancrustaceans, both crustaceomorphs and Hexapoda. Furthermore, it is not uncommon that this multiplicity of sources for new data from opposing research teams can result in different hypotheses for phylogenetic relationships. This situation should not be treated as a defect, or an impediment, but rather as a source for multiple alternative hypotheses—the bases for further data gathering and analyses. Also, one should never view consideration of fossils as a vexing source of noise. Here, too, consideration of multiple hypotheses has proven useful. Often, fossils can produce deeper understanding of the paleodiversity of body plans. Nevertheless, some fossil groups still remain as enigmas, such as Thylacocephala. But even fossils incompletely understood can help fill in gaps in knowledge of paleobiodiversity that can prove useful, for example, in analyzing the the origin and early evolution of Hexapoda. Old ideas about pancrustacean evolution have served the field well, but results derived from all data inputs should be embraced.