The Phylogenetic Relationships And Evolutionary History Of Titanosauriform Sauropod Dinosaurs

MANNION, PHILIP D.; UPCHURCH, PAUL; POROPAT, STEPHEN F.; ALLAIN, RONAN; GONZÁLEZ RIGA, BERNARDO J.

Munich

Congreso; 15th Annual Meeting of the Association of European Vertebrate Palaeontologists; 2017

Association of European Vertebrate Palaeontologists

Titanosauriforms represent the most diverse clade of sauropod dinosaurs, with >120 species, a global distribution, and a Late Jurassic to end-Cretaceous temporal range. Interrelationships of this clade are poorly understood, especially for derived titanosaurs; however, a wealth of new data provides an opportunity to remedy this problem. Based on first-hand study of taxa and an extensive review of the literature, here we present a revised phylogenetic analysis focused on titanosauriforms, comprising 88 taxa (including 30 titanosaurs) scored for 451 characters, many of which are novel to this study. After pruning several unstable and highly incomplete taxa, analysis in TNT produces a fairly well-resolved topology. The ?French Bothriospondylus? is recognised as a new genus of brachiosaurid, and is the earliest known (Oxfordian) titanosauriform. A putative South American brachiosaurid (Padillasaurus) is instead recovered as a somphospondylan. Many analyses, including previous iterations of this matrix, have recovered a titanosaurian clade consisting of taxa known primarily from skulls. Our results place Sarmientosaurus as a basal titanosaur and remove Rapetosaurus from Nemegtosauridae, although Tapuiasaurus is still allied with the latter clade. We recover a diverse clade of Late Cretaceous South American (including Antarctosaurus, Epachthosaurus and Mendozasaurus) and Indo-Madagascan (Jainosaurus, Vahiny) lithostrotian titanosaurs. The latest Cretaceous Eurasian taxa Lirainosaurus and Opisthocoelicaudia cluster with the North American Alamosaurus, nested within a clade of South American (including Aeolosaurus, Baurutitan and Saltasaurus) and Indo-Madagascan (Isisaurus, Rapetosaurus) lithostrotians. Biogeographic analysis indicates that many titanosaur lineages were widespread by the late Early Cretaceous, with regional extinctions leading to continent-scale endemicity.