This volume comprises 16 invited chapters authored by 29 contributors. As noted by the editors, the chapters represent “seemingly unrelated approaches to the study of avian evolution.” The stated purpose is to “help bridgea gap that has developed between those who study birds as fossils and those who study the living animals.” Once one gets beyond the inexplicable title and the first three chapters, to which I will return, one finds several interesting and thought-provoking chapters that work toward the editors' goal. Others are less successful.
The book is divided into four parts of unequal depth, with each chapter comprising a review of its topic. In this sense it is a useful tool, in that one can find an updated list of references for each topic, although the lists are often as notable for what is left out as for what is included. The three themes that I found most interesting are the reviews of specific avian groups, the evolution of certain avian traits, and the discussions of current methodologies for understanding avian evolution. Of the first, a review of the giant, presumably marine “pseudo-toothed,” or “false-toothed,” odontopterygiform birds by E. Bourdon and a review of penguins by D. Ksepka and T. Ando are highlights. Focusing on a cladistic analysis instead of possible life-history traits and functional morphology, the chapter by H. Alvarenga et al. on phorusrhacids, the “terror birds” of South America, is disappointing. Finally, F. Barker presents hypotheses of phylogeny and diversification of passerines, with a heavy emphasis on molecular models.
For the avian traits, S. Walsh and A. Milner provide a detailed and engaging review of the evolution of the avian brain and senses. A discussion of the brain of Archaeopteryx illustrates how far Jurassic birds had advanced from their nonvolant archosaurian ancestors. On the basis of avian brain anatomy, the authors even pose the question, which is novel for this volume, of whether some so-called theropods were really flightless birds. An elementary review of flight in modern birds is presented by B. Tobalske et al., with an unfortunate nod to the strange hypothesis that chicks of highly derived neornithine birds are good models for the evolution of flapping flight. C. Organ and S. Edwards review what they consider to be major events in avian genome evolution, while stressing that too few avian genomes are known to draw any conclusions regarding genome evolution in birds. B. Lindow reviews earlier papers that discuss avian evolution across the Cretaceous— Paleogene boundary but offers no new information or insights into this critical period of explosive avian diversification. A chapter by G. Kaiser on diversity in marine and aquatic birds is best avoided. G. Dyke and E. Gardiner discuss what the fossil record might tell us about when the neornithine radiation began, remarkably proclaiming that little progress in understanding avian evolution has occurred in the past 50 years!
The third theme is split between two parts of the book. On the one hand, the late B. Livezey provides a thorough evaluation of the contrasts and commonalities between morphological and molecular methodologies for arriving at avian phylogenies. As a counterpoint, J. Brown and M. Van Tuinen provide an overview of molecular phylogenetic dating techniques and their application to studies of neornithine origins and evolution. Ironically, both contributions, and other chapters in the book, tout rigorous phylogenetic analyses as key to constructing avian phylogenies while failing to recognize that both morphological and molecular phylogenetic methodologies are rooted in subjective decisions as to what is or is not important as data and how to interpret “characters.” The rigor of subsequent analyses is in the eye of the beholder.
The book ends with a chapter on the state of the world's birds and the future of avian diversity by G. Thomas. The picture presented is that of a double-edged sword of human habitat destruction and climate change wreaking havoc on avian species diversity. Certainly, avian diversity faces a bleak and uncertain future, which is perhaps the most important reason for documenting current diversity and distributions to the maximum extent possible. Soon, the only records of too many modern species and the evolutionary history recorded in their genes will be limited to specimens preserved in museum collections.
To return to the inexplicable title and first chapters, although the BAD (birds-are-dinosaurs) hypothesis is de rigueur in some circles, there remains no meaningful, much less substantive or definitive, evidence that birds are derived from dinosaurs. The statement presented on the book's back cover that controversies over avian origins “have been swept away” is nonsense. Indeed, so many Mesozoic birds have been mistakenly characterized as theropod dinosaurs (e.g., Caudipteryx, Microraptor, and Anchiornis) that it will probably take decades to sort them out and arrive at an accurate picture of avian origins. This is not the place to enumerate the numerous faulty arguments upon which the BAD hypothesis is based, but because two are prominent in the first chapters, it might be informative to see just how obfuscatory characters purported to support the BAD hypothesis have become.
First, “dinofuzz" is a hair-like integumentary covering that is, as noted by P. Makovicky and L. Zanno, found in several dinosaur groups, and even pterosaurs. It is present on some theropods, so it is interpreted by BAD supporters as a precursor to avian feathers. Except in fertile imaginations, however, no transitional phases between dinofuzz and feathers exist, not even among the hundreds of splendid Mesozoic fossils from China. Integumentary coverings are not included in the “comprehensive” cladistic analysis of J. O'Conner et al.
Second, the homologies of the digits of the avian manus have been argued over seemingly forever. Recently, however, three different laboratories, working independently and with different techniques, demonstrated that avian digits are II-III-IV, not I-II-III as in theropods. Makovicky and Zanno perfunctorily dismiss these data, whereas O'Conner et al. acknowledge the possibility that II-III-IV is correct for birds, but strangely extend the II-III-IV enumeration to theropod dinosaurs. In their text and cladistic analysis, however, they treat the digits as I;II;III, which clearly corrupts their results. There are no functional similarities between the wrists of theropods and those of birds, so correctly identifying digit homologies is only one step toward a more accurate analysis.
Technically, the book is reasonably well produced. Nonetheless, there is an irritatingly large number of misspellings, missing words, and lapses in punctuation. Most of the illustrations of avian fossils are printed at such a small scale as to be of little value, which is unfortunate because they could have been very informative. Conversely, color figures are also presented in black-and-white in their respective chapters, and some figures appear three times. A glossary and index are included, although some of the glossary definitions are erroneous, which is bad for students.
All in all, the book might be useful for those who wish to keep abreast of various aspects of avian evolution, especially specialists in the field and those with specific interests in the topics covered. Given its relatively high cost and unbalanced presentation, I doubt that it will achieve the purpose for which it was intended. As J. Cracraft remarks in his foreword, the book might be a place for young investigators to get their feet wet, but I would caution them not to drink the water.
