The Complete Dinosaur

33. Disease in Dinosaurs

667 Disease in Dinosaurs Elizabeth Rega 33 Dinosaur disease is an intriguing subject for the scholar and public alike, resulting from the combination of often bizarre deformity with already charismatic mega fauna. Throw in the “CSI” thrill of solving an ancient cold case, and the result is a heady mix, but one which runs the risk of substituting headlines for scientific rigor. To paraphrase the famed fictional sleuth Sherlock Holmes, the scientific approach should be to define the plausible range of possibility while excluding the impossible and arguing against the improbable . While attempting to avoid pedantism, this approach to paleopathology will characterize the review contained in this chapter. Observations of ancient disease are as old as the study of fossils themselves . Dramatic examples of bone pathology attracted attention from the earliest days of paleontology (Esper 1774), with descriptions and diagnoses of abnormal bone scattered throughout both the scholarly and popular literature. Conclusions about the effect of disease on dinosaurian behavior, diet, locomotion, and the even the role of pathology in extinction are ideally based on complete skeletons, but more commonly conclusions are made from isolated specimens of diseased bone. Determining the pathological requires a thorough knowledge of the normal. Because recognition of normal variation necessitates a larger sample than just one bone or individual, deformity due to disease has been cited as grounds to challenge the establishment of new taxa displaying unexpected features. No less a scientist than pathologist and physician Rudolf Virchow famously (and mistakenly) attributed the morphology of the original Neanderthal skeleton to the ravages of arthritis, premature suture fusion, and rickets on a modern human (Rosen 1977; Virchow 1872). More recently, the protracted debate over the novel morphology of the Liang Bua hominids from the island of Flores hinged on whether the LB1 cranium manifests normal features of a new species or pathological ones of Homo sapiens (Argue et al. 2006; Brown et al. 2004; Gordon et al. 2008; Martin et al. 2006). The term paleopathology has its origins in the study of extinct nonhuman vertebrates. Virchow has been identified as the “first genuine paleopathologist ” (Klebs 1917; Scarani 2003, 95), although several earlier researchers documented pathologies from paleontological and archaeological contexts (Esper 1774; Eudes-Deslongchamps 1838; von Walther 1825; see Cook and Powell 2006). Ruffer claims credit for the term’s creation (1914). He was identified as its originator by Klebs (1917) and Moodie (1918a), and modern sources (Weiss 2000) continue to perpetuate this error. A (Brief) History of Paleopathology in Paleontology Elizabeth Rega 668 In fact, Aufderheide and Rodriguez Martin (1998) attribute the first use of the term to physician and amateur ornithologist R. W. Shufeldt, who used it to describe the study of “all diseased or pathological conditions found fossilized in the remains of extinct or fossil animals” (Shufeldt 1893, 679). Shufeldt’s expertise was sought by none other than E. D. Cope in the latter’s search for evidence of predation-related injuries in a large sample of Pliocene bird skeletons. Shufeldt relied less on his experience as a physician and more on his avocational study of avian injuries in assessing the pathologies from this sample, which he found to be surprisingly few in number. He refers to his observations on fracture healing in extant birds to explain ancient fracture, with a clear emphasis on matching the progression and process of injury and avian healing (Fig. 33.1). Shufeldt makes explicit the uniformitarian approach to ancient skeletal pathology: “Animals that lived during the past ages of the world, and now long extinct, must have suffered, it would seem, from many injuries quite similar to those now sustained by their descendants of the present epoch” (1893, 679). As with its geological counterpart, uniformitarianism in paleopathology is predicated on the assumption that past disease processes are identical to those observable in the present day. In a manner later to be characteristic of most paleopathological studies, Shufeldt proceeds to the next level of inference, proposing mechanisms for injury and a hypothesis of wing-fighting behavior that he admits has no parallels in his extant comparative sample. He concludes his brief study by outlining alternative scenarios for injury and underscores the speculative nature of his behavioral conclusions. Paleopathology Originated with Animals Although the discipline of paleopathology has come to be dominated by inquiries into ancient human disease, early texts regarded as seminal to the field focused on pathologies of extinct animals. Pleistocene fauna were the subject of the very earliest paleopathological reports as cave excavation gained prominence (Esper...