A Cold Look at Paleophysiology

Although science demands compromise be­ tween the proposition of imaginative hypotheses and the availability of data with which to test them, paleophysiologists have always accorded themselves a great deal of leeway in this area. Data have been few and hard to come by, and their interpretation not readily subject to veri­ fication. Accordingly, our early notions about dinosaur physiology and its adaptive signifi­ cance, like many investigations within the pur­ view of the "adaptationist program" (Gould and Lewontin, 1979), have been arrived at through tacit consensus rather than empirical rejection of alternative hypotheses. Until recently, the concept of dinosaur physiology with the most adherents has been the "correct" one, and this concept has undergone modification along with shifts in opinion. Thus paleophysiologists have perceived dinosaurs sequentially as hulking, slothful, sluggish, cold-blooded brutes; giant liz­ ard-like ectotherms; and, more recently, inertial homeotherms (Desmond, 1975). Proponents of dinosaur endothermy have changed all that, or so they would have us be­ lieve. Certainly, Bakker, Ostrom, and de Ricqles, and their advocates and detractors, have in recent years amassed a wealth of data to attempt to resolve an intriguing question in paleophysiology. However, the exuberance of these attempts has at times fostered a less than critical analysis of the data and of the structure of the arguments involved. Accordingly, I was pleased to see a volume advertised as a cold look at the warm-blooded dinosaurs. This book has many good points. It is a cur­ rent and comprehensive survey of work on the question of whether dinosaurs may have been ectothermic, endothermic, something in be­ tween, or even something entirely different. It captures both the flavor and substance of what is at times a rather acrimonious debate. Most of the major figures in the controversy expand upon the arguments they have made in the past. Farlow, Beland, and Russell comment on pred­ ator-prey ratios in fossil communities; Spotila examines size-imposed constraints on variation in body temperature; de Ricqles and Hopson summarize their work on bone histology and brain size, respectively. Bakker, Ostrom, and Hotton provide overviews of all data bearing on the question. In addition, some new partic­ ipants join the fray: Roth and Roth review pi­ neal-parietal structure in living and fossil ver­ tebrates; Baur and Friedl use size-metabolism allometry to predict putative consequences of endothermy in dinosaurs; Greenberg, Regal, and Gans stress the highly evolved and complex nature of ectothermy in vertebrates. All of these features make this collection noteworthy. My purpose in this review is to determine if the book as a whole fulfills the promise stated in the title. Does the book provide a critical analysis of the controversy to date? Does it an­ swer the following question: are the data yet sufficient to draw major conclusions regarding thermal and metabolic physiology of dinosaurs, or is additional analysis required? I regret to report that the critique promised by the title is absent. The book is yet another restatement of adversary positions; the critical synthesis called for at this time is lacking. Difficulties lie mainly in the way conclusions are drawn from data; I enumerate these difficulties below. To summa­ rize them, there is real disagreement about def­ initions, the meaning of concepts under discus­ sion, and what questions should be addressed. There are faulty generalizations and errors of fact. All of these problems do not attend every contribution, but they are so widespread as to forestall rigorous tests of hypotheses. Accord­ ingly, the debate is often at cross purposes and therefore exceedingly frustrating to the reader. A "cold" or critical look it is not. Determining criteria for successful dinosaurs. —In essence, the major hypothesis under