Lithostrotia

Abstract: A NEW AND HUGE TITANOSAUR SAUROPOD FROM RIO LIMAY FORMATION (ALBIAN-CENOMANIAN), OF NEUQUEN PROVINCE, ARGENTINA. Argentinosaurus huinculensis gen et sp. nov. is a giant titanosaur sauropod characterized by dorsal vertebrae with large hyposphene-hypantrum bearing extra articulations; bodies of sacral vertebrae 2-5 very reduced; hollow cylindrical ribs; slender tibia 155 cm long. The family Andesauridae is proposed as a new rank to include Andesaurus, Argentinosaurus and Epachthosaurus considering that the presence of hyposphene-hypantrum is a character not recorded in the Titanosauridae sensu Powell (1986). The systematics of the titanosaurs is briefly discussed and the new taxon Titanosauria is proposed to include the families Andesauridae and Titanosauridae.

Abstract: Advanced titanosaurian sauropods, such as nemegtosaurids and saltasaurids, were diverse and one of the most important groups of herbivores in the terrestrial biotas of the Late Cretaceous. However, little is known about their rise and diversification prior to the Late Cretaceous. Furthermore, the evolution of their highly-modified skull anatomy has been largely hindered by the scarcity of well-preserved cranial remains. A new sauropod dinosaur from the Early Cretaceous of Brazil represents the earliest advanced titanosaurian known to date, demonstrating that the initial diversification of advanced titanosaurians was well under way at least 30 million years before their known radiation in the latest Cretaceous. The new taxon also preserves the most complete skull among titanosaurians, further revealing that their low and elongated diplodocid-like skull morphology appeared much earlier than previously thought.

Abstract: . Mendozasaurus neguyelap gen. et sp. nov. is a new titanosaur from the Upper Cretaceous of Neuquen Basin and the first known dinosaur species from Mendoza Province, Argentina. The remains were found in levels provisionally referred to the Rio Neuquen Formation (late Turonian-late Coniacian) of the Neuquen Group. They consist of 22 mostly articulated caudal vertebrae, a dorsal vertebra, numerous disarticulated appendicular bones and osteoderms. Autapomorphies of Mendozasaurusare: (1) subtriangular infrapostzygapophyseal fossae in anterior dorsal vertebrae; (2) postzygapostspinal laminae parallel to the plane of the postzygapophyseal facets in anterior dorsal vertebrae; (3) interzygapophyseal cavity dorsoventrally extended and limited by the spinopostzygapophyseal and spinoprezygapophyseal laminae in anterior caudal vertebrae; (4) middle caudal vertebrae slightly procoelous with reduced posterior condyles displaced dorsally; (5) laminar mid-posterior caudal neural spines with horizontal and straight dorsal border, and anterodorsal corner forming a right angle; (6) large subconic-spherical osteoderms lacking cingulum. A cladistic analysis permits the inclusion of Mendozasaurus within Titanosauridae, according to the phylogenetic definition of this clade. Although this new species exhibits almost all the titanosaurid synapomorphies proposed by some authors, it lacks prominent posterior condyles in middle caudal centra. This and other plesiomorphic traits suggest that Mendozasaurus is a basal titanosaurid, more derived than Malawisaurusin the caudal procoely. Resumen. UN NUEVO TITANOSAURIO (DINOSAURIA, SAUROPODA) DEL CRETACICO SUPERIOR DE LA PROVINCIA DE MENDOZA, ARGENTINA. Mendozasaurus neguyelap nov. gen. et sp. es un nuevo titanosaurio del Cretacico Superior de la Cuenca Neuquina y la primera especie de dinosaurio proveniente de la provincia de Mendoza, Argentina. Procede de niveles asignados preliminarmente a la Formacion Rio Neuquen (Turoniano tardio-Coniaciano tardio) del Grupo Neuquen. Esta representado por 22 vertebras caudales en su mayoria articuladas y numerosos restos desarticulados: una vertebra dorsal, arcos hemales, huesos apendiculares y grandes osteodermos. Son autapomorfias de Mendozasaurus: (1) fosas infrapostzigapofisiales subtriangulares en vertebras dorsales anteriores; (2) laminas postzigapostespinales paralelas a los planos de las facetas articulares de las postzigapofisis en vertebras dorsales anteriores; (3) cavidad interzigapofisial dorsoventralmente extendida y limitada por las laminas espinopostzigapofisial y espinoprezigapofisial en vertebras caudales anteriores; (4) centros caudales medios suavemente procelicos con condilos posteriores reducidos y desplazados dorsalmente; (5) espinas neurales de vertebras caudales medias-posteriores laminares y anteroposteriormente elongadas, con un borde dorsal horizontal y un angulo anterodorsal recto y (6) grandes osteodermos subconicos-subesfericos sin cingulum. Un analisis cladistico permite incluir a Mendozasaurusdentro de Titanosauridae, segun definiciones filogeneticas de este clado. Si bien exhibe casi todas las sinapomorfias propuestas por algunos autores para caracterizar a Titanosauridae, carece de condilos posteriores prominentes en sus vertebras caudales medias. Este y otros caracteres plesiomorficos sugieren que Mendozasaurus es un titanosaurido basal, mas derivado que Malawisaurusen su procelia caudal.