Sauropod dinosaur phylogeny: critique and cladistic analysis

Sauropoda is among the most diverse and widespread dinosaurlineages, having attained a near‐global distribution by the MiddleJurassic that was built on throughout the Cretaceous. These giganticherbivores are characterized by numerous skeletal specializationsthat accrued over a 140 million‐year history. This fascinating evolutionaryhistory has fuelled interest for more than a century, yet aspectsof sauropod interrelationships remain unresolved. This paper presentsa lower‐level phylogenetic analysis of Sauropoda in two parts. First,the two most comprehensive analyses of Sauropoda are critiqued toidentify points of agreement and difference and to create a coreof character data for subsequent analyses. Second, a generic‐levelphylogenetic analysis of 234 characters in 27 sauropod taxa is presentedthat identifies well supported nodes as well as areas of poorerresolution. The analysis resolves six sauropod outgroups to Neosauropoda,which comprises the large‐nostrilled clade Macronaria and the peg‐toothedclade Diplodocoidea. Diplodocoidea includes Rebbachisauridae, Dicraeosauridae,and Diplodocidae, whose monophyly and interrelationships are supportedlargely by cranial and vertebral synapomorphies. In contrast, thearrangement of macronarians, particularly those of titanosaurs,are based on a preponderance of appendicular synapomorphies. The purportedChinese clade ‘Euhelopodidae’ is shown to comprisea polyphyletic array of basal sauropods and neosauropods. The synapomorphiessupporting this topology allow more specific determination for themore than 50 fragmentary sauropod taxa not included in this analysis.Their distribution and phylogenetic affinities underscore the diversityof Titanosauria and the paucity of Late Triassic and Early Jurassicgenera. The diversification of Titanosauria during the Cretaceousand origin of the sauropod body plan duringthe Late Triassic remain frontiers for future studies. © 2002The Linnean Society of London, Zoological Journal of the LinneanSociety, 2002, 136 , 217?276.