The late Willi Hennig was director of phylongenetic research at the State Museum of Natural Science, Stuttgart. His honors included the Gold Medal of the Linnaean Society and the Gold Medal for Distinguished Achievement in Science of the American Museum of Natural History

"A landmark in the development of cladistic systematics." - Biological Abstracts "This book should be read by all practicing systematists as well as other biologists interested in the analysis of relationships of organisms."-The Biologist "The ideas put forth in this far-reaching study, and the author's treatment of the subject, should introduce new perspectives to scientists in all areas of biology."- -Scientia "English-speaking systematists should be glad to have an opportunity to be exposed to the views of the foremost proponent of the cladistic school. Indeed, no thinking systematist can afford not to have read this volume."-Robert R. Sokal, Science "This is required reading for all interested in biosystematics."-Plant Life "Phylogenetic Systematics is a difficult, stimulating, and controversial work ... indispensable to the thoughtful systematist."-Journal of Paleontology