Problematic fossils--those groups of organisms that do not fit conveniently into any existing phylum--play a pivotal role in the reconstruction of the history of life, being in effect "early experiments." This lavishly illustrated volume provides careful analyses and descriptions--in anatomical, functional, and developmental terms--of most of the major problematic fossil taxa. Sixteen original papers, written by internationally recognized scholars, discuss the features that make these taxa problematic and that provide clues to their phylogenetic relationships. Since Precambrian groups have been well covered in the existing literature, Hoffman and Nitecki focus on Paleozoic, and especially Early Paleozoic organisms, although Precambrian biota are also discussed.

Neutral models are constructed to help scientists understand complex patterns of form, structure, or behavior that may not be observed directly. In this unique volume, eight distinguished scientists present a comprehensive study of the use of neutral models in testing biological theories. They describe the principles of model testing and explore how they are applied to research in molecular biology, genetics, ecology, evolution, and paleontology. In addition to the editors, the contributors include Stephen Stigler, David Raup, Paul Harvey, L.B. Slobodkin, Stuart Kauffman, William Wimsatt, and James Crow.