Claus Nielsen, Director, Zoological Museum, Copenhagen.
"Claus Nielson has compiled an extremely impressive review of the major features of animal phyla, and within a phylogenetic framework. This masterpiece integrates both developmental and adult characteristics into a synthesis that will form THE fundamental reference for the evolution of animal phyla for at least the next decade--a truly impressive accomplishment. This work not only offers a complete phylogenetic analysis of all animal phyla, it contains new hypotheses of relationships where such rearrangements are supported by clear, unambiguous synapomorphies. . . .This book has great potential as a university classroom text. Although this does not appear to be the intention of the text, learning about the progression of animal complexities could not be presented in a more lucid manner for students."-- Robert W. Murphy, The Canadian Field-Naturalist
"Nielsen has prepared an exceptionally valuable, concise book. . .A must for all zoologists and biologists engaged in teaching the systematics of animal groups." --Choice