Osteology of the Late Cretaceous Argentinean sauropod dinosaur Mendozasaurus neguyelap: implications for basal titanosaur relationships.

GONZÁLEZ RIGA, BERNARDO J.; MANNION, PHILIP D.; POROPAT, STEPHEN F.; ORTIZ DAVID, LEONARDO D.; CORIA, JUAN PEDRO

ZOOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

Oxford University Press

Año: 2017

0024-4082

The titanosaurian sauropod dinosaur Mendozasaurus neguyelap isrepresented by several partial skeletons from the Upper Cretaceous SierraBarrosa Formation in Mendoza Province, Argentina. A detailed revisionallows us to firmly establish its position within Titanosauria, as well asenabling an emended diagnosis. New remains demonstrate that thepresacral vertebrae of Mendozasaurus were not unusually shortanteroposteriorly, with this compression instead resulting from taphonomiccrushing. Mendozasaurus was incorporated into an expanded version of atitanosauriform-focussed phylogenetic data matrix, along with severalother contemporaneous South American titanosaurs. The resultant datamatrix comprises 84 taxa scored for 423 characters and and our analysisrecovers Mendozasaurus as the most basal member of a diverseLognkosauria, including Futalognkosaurus and the gigantic titanosaursArgentinosaurus, Notocolossus, Patagotitan and Puertasaurus.Lognkosauria forms a clade with Rinconsauria (Muyelensaurus +Rinconsaurus), with Epachthosaurus and Pitekunsaurus recovered at thebase of this grouping. A basal lithostrotian position for this South Americanclade is well supported, contrasting with some analyses that have placedthese taxa outside of Lithostrotia or closer to Saltasauridae. The sisterclade to this South American group is composed of an array of near-globaltaxa, and supports the hypothesis that most titanosaurian clades werewidespread by the Early?middle Cretaceous.