1. Department of Anatomical Sciences, Health Sciences Center, State University of New York, Stony Brook, New York 11794, USA
2. Present address: Department of Paleontology, Science Museum of Minnesota, 120 W. Kellogg Boulevard, St Paul, Minnesota 55102, USA; and Macalester College, Geology Department, St Paul, Minnesota 55105, USA.

Correspondence to: Kristina Curry Rogers¹ Correspondence and requests for materials should be addressed to K.C.R. (e-mail: Email: krogers@smm.org).

Abstract

The Titanosauria, the last surviving group of the giant sauropod dinosaurs, attained a near-global distribution by the close of the Cretaceous period (65 Myr ago). With the exception of a few new discoveries in Argentina^{1, 2, 3}, most titanosaurs are known only from fragmentary postcranial skeletons and rare, isolated skull elements^{4, 5, 6, 7, 8, 9}. Here we describe the most complete titanosaur yet discovered. Rapetosaurus krausei gen. et sp. nov., from the Maevarano Formation of Madagascar, provides a view of titanosaur anatomy from head to tail. A total-evidence phylogenetic analysis supports a close relationship between brachiosaurids and titanosaurs (Titanosauriformes^{10, 11, 12, 13}). The inclusion of cranial data from Rapetosaurus also lays to rest questions concerning the phylogeny of the enigmatic Mongolian genera Nemegtosaurus and Quaesitosaurus^{14, 15}. In spite of their elongated, diplodocoid-like skulls, all three taxa are now firmly nested within Titanosauria.