In lieu of an abstract, here is a brief excerpt of the content:

SAUROPOD STUDIES FROM OWEN TO THE PRESENT This year marks the one hundred sixty-fourth anniversary of Richard Owen’s (1841) description of the first sauropod—Cetiosaurus, the “whale lizard”—on the basis of vertebrae and limb elements from localities across England. Although these remains “had been examined by Cuvier and pronounced to be cetaceous” (Buckland 1841:96), Owen (1841:458–459) demonstrated the saurian affinities of Cetiosaurus on the basis of several features, including the absence of epiphyses (growth plates) on caudal vertebrae (fig. 1.1). He differentiated Cetiosaurus from other extinct saurians on the basis of its large size and characteristics of its vertebrae (see Upchurch and Martin 2003:215). Owen (1841:462) concluded his initial description with this assessment : “The vertebræ, as well as the bones of the extremities, prove its marine habits . . . the surpassing bulk and strength of the Cetiosaurus were probably assigned to it with carnivorous habits, that it might keep in check the Crocodilians and Plesiosauri.” He regarded Cetiosaurus as a crocodilian by the “form of the long bones” and “the toes being terminated by strong claws” (Owen 1842:102), but this assessment was based on limited anatomical evidence (Owen 1875:27). Key data emerged with the discovery of abundant Cetiosaurus bones in Oxfordshire by John Phillips. Thomas Huxley examined this “splendid series of remains” before the publication of Phillips’ (1871) monograph and was the first to place Cetiosaurus within Dinosauria (Iguanodontidae [Huxley, 1869:35]). Phillips (1871) interpreted Cetiosaurus as a planteating dinosaur and hypothesized that its limb bones were “suited for walking.” He could not rule out the possibility that it was amphibious, however, concluding that it was a “marsh-loving or riverside animal.” Owen (1875:27) later acquiesced , referring Cetiosaurus to the Dinosauria because of its four sacral vertebrae. He admitted that it may have had some terrestrial capabilities but concluded that Cetiosaurus was an estuarine or marine animal based on its “organ of swimming ,” the tail (Owen 1875:41). These early interpretations, based on somewhat limited samples, were followed by the discovery of abundant sauropod skeletons in western North America and eastern Africa during 15 One Overview of Sauropod Phylogeny and Evolution Jeffrey A. Wilson the late nineteenth and early twentieth centuries. O.C. Marsh and E.D. Cope described numerous new and well represented sauropod genera from the Morrison Formation of the western United States, including the first complete sauropod skull (Diplodocus [Marsh 1884]), reconstructions of the skeletons of Brontosaurus by Marsh (1883; fig. 1.2) and Camarasaurus by Cope (Osborn and Mook, 1921:pl. 82; fig. 1.2), and the first mount of a complete sauropod skeleton (Diplodocus [Anonymous 1905]). These discoveries provided the first examples of ontogenetic variation and phylogenetic diversity in sauropods. Later, German expeditions to East Africa (present-day Tanzania) produced sauropod material rivaling that from North America. Janensch and others led field crews at Tendaguru, where they collected more than 235,000 kg of fossils (Maier 2003:105) that represented many new genera described over the course of 50 years (e.g., Janensch, 1914, 1929a, 1935–36, 1950, 1961). The abundance and diversity of sauropod remains unearthed in North America and Africa not only answered many of the queries posed by early sauropod researchers (e.g., dinosaurian affinities and terrestrial habits of sauropods) but also posed new ones. One of the major controversies that extended across the Atlantic surrounded the posture of sauropods. American scientists favored an upright, columnar posture, whereas their German colleagues deemed a lacertilian pose more appropriate (Holland 1910; Desmond 1975). A second question, less controversial but farther-reaching, emerged from the study of these two large collections of sauropod material—How should sauropod diversity be classified? TRADITIONAL CLASSIFICATION When Marsh (1878) coined the suborder Sauropoda, it included only a single family, Atlantosauridae. Several of the features Marsh (1878:412) listed in that initial diagnosis of Sauropoda are now well-corroborated synapomorphies for the group or for more exclusive sauropod subgroups that were not identified at the time of Marsh’s writing. Marsh invented new families to accommodate the increasing sauropod diversity revealed by new discoveries worldwide (e.g., Atlantosauridae, Morosauridae, Diplodocidae, Pleurocoelidae, Titanosauridae). The formal familial diagnoses for these groups (Marsh 1884, 1895) also recognized features currently considered synapomorphies for sauropod subclades. These diagnoses, however, did not resolve how these groups were interrelated; Marsh’s ranked classifications did not function as hypotheses of evolutionary descent. On the basis of his burgeoning Tendaguru collection, Janensch (1929a) produced a very different classification of...

Share