A Modern Overview of Crustacean Biogeography: Evolution and Biogeography Review

Martin Thiel continues his ambitious and successful role as series editor for Oxford’s Natural History of the Crustacea. Volume 8 (Evolution and Biogeography) includes 18 chapters that discuss crustacean evolution and emergent patterns (and causal mechanisms) underlying the biogeography of Crustacea in marine, freshwater, terrestrial, and subterranean habitats. As is often the case with edited volumes, some chapters are stronger than others, but overall, this is a book most invertebrate zoologists, marine biologists, and biogeographers will want on their shelves. Because of its emphasis on review chapters, the volumewill be especially useful for beginning researchers and those who are not crustacean specialists. Five chapters focus on the evolution of Crustacea. Among the strongest is Shane Ahyong’s summary of current views on crustacean evolution (“Evolution andRadiation of Crustacea”), noting that over the past two decades, our phylogenetic perspective has shifted from a long-bodied, serially homonomous ancestry (as seen in remipedes and cephalocarids; an idea promoted by Howard Sanders, Bob Hessler, and Fred Schram and one that many of us “cut our teeth on”) to a short-bodied, possibly ostracod-like ancestry similar to Cambrian stemand crown-group fossil forms. Ahyong correctly acknowledges the importance of the Orsten fauna as a key lens through which to understand the early evolution of Crustacea, noting that the oldest definitive crustacean fossils are upper Cambrian Orsten of Sweden—small, just millimeters in length, but exquisitely preserved specimens owing to their phosphatic preservation. Earlier ideas of long, serially homonomous ancestry had been influenced by two scientifically flawed lines of reasoning. First was an underlying notion that evolution moves from simple toward more complex. Second was a reliance on largely untestable narratives of ur-crustacean bodymorphology as a starting point (i.e., the hypothetical ancestor approach). The new view, of Pancrustacea comprising the two great clades Oligostraca and