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Evolving Form and Function: Fossils and Development Proceedings of a symposium honoring Adolf Seilacher for his contributions to palaeontology, in celebration of his 80th birthday

Reviewed by Stephen Q. Dornbos

Edited by Derek E.G. Briggs Peabody Museum of Natural History Yale University, New Haven, Connecticut, 2005, 288 pp. ISBN-10: 0-912532-72-6, $144.98 This book is a compilation of papers derived tion, as well as providing new evidence, primarily from a meeting held April 1-2, 2005 at Yale Univer- from trace fossils, for the life sity to honor Adolf Seilacher’s contributions to our modes of some well-known understanding of the evolution of form and func- Ediacaran organisms. tion. The quality and diversity of the chapters in Based on associated serial this book certainly create a volume worthy of resting traces, for example, Seilacher’s legacy in this field. Dickinsonia and Yorgia are Derek Briggs, the editor, starts things off with interpreted as using their a chapter summarizing Seilacher’s contributions to lower surfaces to decom- the study of form and function in fossil organisms. pose the underlying micro- Of particular interest is his emphasis on the impor- bial mat surface and absorb tance of phylogeny and architecture in the con- the released nutrients. struction of a broad range of organisms, from Placing his thoughts in vendobionts to crinoids. The chapter also contains an economic framework, an Appendix of the complete publications of Doug Erwin takes on the origin of animal body Seilacher, an invaluable resource. plans in the next chapter. Among other things, he The second chapter, by Karl Niklas, centers reviews the environmental changes thought to on the morphogenesis and biomechanics of mod- have been taking place during the radiation and the ern plants, concluding that plants increase their current ideas about the early developmental biol- root mass and strength while decreasing their ogy of bilaterians. Erwin concludes that the most height, leaf area, and the strength and stiffness of likely explanation for the Cambrian radiation lies the stem in response to mechanical disturbance. somewhere in the ecological interactions of early This response helps the individual plant survive, animals. but hinders its reproductive capabilities. Some Phil Donoghue and Xiping Dong next focus on reproduction is apparently better than none at all. the Ediacaran-Cambrian fossil record of animal Jim Gehling, Mary Droser, Sören Jensen, and embryos. They begin by reviewing the embryos Bruce Runnegar author the next chapter, which preserved in the Ediacaran Doushantuo Formation focuses on the form and function of Ediacaran and the Lower Cambrian Kuanchuanpu Formation, organisms. They review Ediacaran fossil preserva- both of south China, as well as the global fossil

Dornbos, Stephen Q. 2006. [Review of Briggs, Derek E.G., ed., Evolving Form and Function: Fossils and Development Proceedings of a symposium honoring Adolf Seilacher for his contributions to palaeontology, in celebration of his 80th birthday] Palaeontologia Electronica, Vol. 9, Issue 2, R4, 3pp. 236kb; http://palaeo-electronica.org/toc9_2.htm DORNBOS: EVOLVING FORM AND FUNCTION record of the Lower Cambrian–Lower Ordovician Paleozoic and post-Paleozoic forms. Paleozoic embryo Markuelia. The authors conclude that, echinoids have different numbers of columns of based on the fossil record, there is reason to ques- plates in their test but similar body shapes, tion the primitive nature of indirect development whereas post-Paleozoic echinoids have the same and that the temporal range of fossil embryos is numbers of columns of plates in their test but have unlikely to expand much with future exploration. a diverse range of body shapes. Smith attributes The mineralized skeletons of early animals is this change to two innovations: a shift from growth the focus of Stefan Bengtson’s chapter. After through plate addition to growth through plate reviewing the skeletonization of early animals, accretion and a shift to plate production earlier in including discussions of small shelly fossils, gen- ontogeny, locking in the adult plate positions at an eral mineralization processes, and coelosclerito- early stage. phorans, Bengtson argues that the coelosclerite Geerat Vermeij authors the next chapter, the skeleton may have been a plesiomorphic character focus of which is the evolution and function of shell of early bilaterians. envelopment in molluscs. Vermeij provides a syn- Ediacaran trace fossils are the subject of the thesis of published information and new observa- chapter Mary Droser, Jim Gehling, and Sören tions that reveal shell envelopment by the foot in Jensen. They briefly review the Ediacaran trace marine and freshwater molluscs occurs repeatedly fossil record and then discuss criteria for identifying in 47 clades, but is rare or absent in other clades. trace fossils and the taphonomic implications of Clades exhibiting shell envelopment share certain mat-bound Ediacaran substrates. Using these cri- physiological and ecological traits and tend to teria and keeping in mind the nature of typical Edi- develop this innovation during warm, productive acaran substrates, the authors then evaluate four periods. examples of described Ediacaran trace fossils and Venturing into the vertebrate realm for the first determine that three of them are unlikely to be time in this volume, Jennifer Clack authors the next traces. They therefore conclude that the diversity chapter about the fish-tetrapod transition. Through of Ediacaran trace fossils has traditionally been a systematic review of the latest results, Clack exaggerated. shows how increased knowledge of the fish-tetra- Nigel Hughes examines the early develop- pod transition fossil record reveals changes to the mental biology of trilobites in the next chapter, head for increased ability to breathe air, among focusing on the number of adult thoracic segments. other things, and changes to the pectoral skeleton, He finds that there is quite a bit of plasticity in this also potentially related to the increased ability to character in basal trilobites, but that it stabilizes in breathe air. The fossil record has also constrained later taxa. One possible explanation for this trend the evolution of tetrapods to the Middle to Late is that increased trunk regionalization, and the Devonian and likely has more information in store accompanied stabilization of thoracic segment for future researchers. number, provided more advantages than plasticity Richard Prum continues the vertebrate theme, in this character. but instead considers the functional evolution of Arthropods are also the subject of the next feathers. The central point of this chapter is that chapter by Matthew Giorgianni and Nipam Patel. modern studies of feather development combined Serving as a general review, their attention is par- with recent fossil discoveries indicate that complex ticularly placed on the latest results regarding the feathers first evolved in the theropods for other pur- evolution and development of arthropod append- poses and were later co-opted for flight; a textbook ages. Building from the molecular and genetic example of exaptation. studies of Drosophila, the authors discuss append- Appropriately, Adolf Seilacher himself pro- age development in a diverse array of arthropod vides the capstone chapter of this volume. His groups. They conclude that arthropod appendage chapter centers on the constructional morphology diversity in underlain by a conserved Proximal-Dis- of secondary soft-bottom dwellers, and includes his tal axis patterning mechanism, and that future stud- standard classic illustrations and innovative ideas. ies of new model arthropods should increase our Considering a broad range of organisms (including understanding of how this limb diversity evolved. Paleozoic brachiopods, bivalves, gastropods, ser- In the next chapter, Andrew Smith discusses pulids, corals, sponges, crinoids, bryozoans, and the evolution of growth and form in echinoids, pay- cirripedes), Seilacher defines and examines the ing special attention to the role of changes in plate guilds within secondary soft-bottom dwellers, each addition and plate accretion as growth strategies in of which provides a different strategy for stabilizing

2 PALAEO-ELECTRONICA.ORG the organism on soft substrates. These guilds each of which is cogently reviewed, analyzed, and have different ecomorphs for each taxonomic discussed in their respective chapters. In this man- group because of their differing phylogenetic con- ner, the volume is a fitting tribute to Seilacher’s straints, and some are even excluded from certain work in this field, which is also known for its guilds because of these constraints. Seilacher con- astounding breadth and depth. I would recom- cludes that future constructional morphology stud- mend this book to any professional paleontologist ies should involve the reconstruction of or graduate student, as it would be a worthy addi- “adaptational road maps” combined with cladistic tion to any of their libraries. analyses. As you can probably tell by now, this volume PE Review Number: 9.2.4R serves up an exceptionally broad range of topics, Copyright: Coquina Press 2006

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