Avanza la preparación del primer ejemplar de dinosaurio terópodo recuperado recientemente en la última campaña paleontológica del MAU en La Invernada. Entre los materiales que ya han sido preparados se cuentan: varias costillas cervicales y dorsales, además de vértebras caudales y cervicales. En estos días esta finalizando la preparación de los restos craneanos, que si bien no se encuentra completo, aportarán relevante información. Si bien, aún queda mucho material sin preparar en el laboratorio del museo, y seguramente por extraer del campo, los elementos que ya se disponen ponen en clara evidencia que el ejemplar corresponde a un abelisaurio el cual habría alcanzado unos 5 m de longitud. Los abelisaurios son un grupo de dinosaurios terópodos principalmente gondwánicos, es decir, habitaron el supercontinente de Gondwana, conformado por Sudamérica, África, India, Australia y la Antártida. Recientemente se ha dado a conocer un nuevo abelisaurio, Arcovenator escotae, el primero proveniente de Europa, lo que sugiere algún tipo de conexión biogeográfica entre Europa y Africa a finales del Cretácico. El abelisaurio de La Invernada, proviene de niveles de la Formación Bajo de la Carpa, los mismos niveles de donde fueron recuperados en la misma campaña a unos 300 m de disntancia, al menos dos ejemplares de dinosaurio sauropodo titanosaurio. Estos materiales aportan interesante información respecto de una asociación faunística donde queda demostrado quien cumplía el papel de depredador y quién el de presa. En la medida que los fósiles sean preparados, daremos a conocer más información respecto de este nuevo carnívoro patagónico.

Foto ilustrativa: Sergey Krasovskly


Fernando E. Novas, Federico L. Agnolín, Martín D. Ezcurra, Juan Porfiri and
Juan I. Canale

 Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, consisting of 31 nominal species belonging to singleton taxa and six families: Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptoridae nov. fam., Alvarezsauridae, and Unenlagiidae. They provide anatomical information that allows improved interpretation of theropods discovered in other regions of Gondwana. Abelisauroids are the best represented theropods in Patagonia. They underwent an evolutionary radiation documented fromthe Early Cretaceous through tothe latest Cretaceous, and are represented by the clades Abelisauridae and Noasauridae. Patagonian carcharodontosaurids are known from three taxa (Tyrannotitan, Giganotosaurus and Mapusaurus), as well as from isolated teeth, collected from Aptian to Cenomanian beds. These allosauroids constituted the top predators during the mid-Cretaceous, during which gigantic titanosaur sauropodswere the largest herbivores. Megaraptorans have become better documented in recent years with the discovery of more complete remains. Megaraptor, Aerosteon and Orkoraptor have been described from Cretaceous beds from Argentina, and these taxa exhibit close relationships with the Aptian genera Australovenator, from Australia, and Fukuiraptor, from Japan. The Gondwanan megaraptorans are gathered into the newfamily Megaraptoridae, and the Asiatic Fukuiraptor is recovered as the immediate sister taxon of this clade. Although megaraptorans have been recently interpreted as members of Allosauroidea, we present evidence that they are deeply nested within Coelurosauria. Moreover, anatomical information supports Megaraptora as more closely related to the Asiamerican Tyrannosauridae than thought. Megaraptorans improve our knowledge about the scarcely documented basal radiation of Gondwanan coelurosaurs and tyrannosauroids as awhole. Information at hand indicates that South America was a cradle for the evolutionary radiation for different coelurosaurian lineages, including some basal forms (e.g., Bicentenaria, Aniksosaurus), megaraptorans, alvarezsaurids less derived than those of Laurasia, and unenlagiids, revealing that Gondwanan coelurosaurs played sharply differing ecological roles, and that theywere taxonomically as diverse as in the northern continents. The unenlagiids represent an endemic South American clade that has been recently found to be more closely related to birds than to dromaeosaurid theropods. Analysis of the theropod fossil record from Gondwana shows the highest peak of origination index occurred during the Aptian-Albian and a less intense one in the Campanian time spans. Additionally, peaks of extinction index are recognized for the Cenomanian and Turonian-Coniacian time spans. In comparison, the Laurasianpattern differs fromthat of Gondwana in the presence of an older extinction event during the Aptian-Albian time-span and a high origination rate during the Cenomanian time-bin. Both Laurasian and Gondwanan theropod records show a peak of origination rates during the Campanian.

Novas, F.E., Agnolín, F.L., Ezcurra, M.D., Porfiri, J.D., Canale, J.I. 2013. Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia. Cretaceous Research 45:174–215.

William Irvin Sellers1, Lee Margetts, Rodolfo Aníbal Coria, Phillip Lars Manning

Sauropod dinosaurs are the largest terrestrial vertebrate to have lived on Earth. This size must have posed special challenges for the musculoskeletal system. Scaling theory shows that body mass and hence the loads that must be overcome increases with body size more rapidly than either the ability of the muscles to generate force, or the ability of the skeleton to support these loads. Here we demonstrate how one of the very largest sauropods, Argentinosaurus huinculensis (40 metres long, weighing 83 tonnes), may have moved. A musculoskeletal model was generated using data captured by laser scanning a mounted skeleton and assigning muscle properties based on comparative data from living animals. Locomotion is generated using forward dynamic simulation to calculate the accelerations produced by the muscle forces, coupled with machine learning techniques to find a control pattern that minimises metabolic cost. The simulation demonstrates that at such vast body size, joint range of motion needs to be restricted to allow sufficient force generation for an achievable muscle mass. However when this is done, a perfectly plausible gait can be generated relatively easily. Whilst this model represents the best current simulation of the gait of these giant animals, it is likely that there are as yet unknown mechanical mechanisms, possibly based on passive elastic structures that should be incorporated to increase the efficiency of the animal`s locomotion. It is certainly the case that these would need to be incorporated into the model to properly assess the full locomotor capabilities of the animal.

Sellers, W.I., Margetts, L., Coria, R.A. and Manning, P.L. 2013. March of the Titans: The Locomotor Capabilities of Sauropod Dinosaurs. PLoS ONE 8(10): e78733. doi:10.1371/journal.pone.0078733

Lucio M. Ibiricu, Gabriel A. Casal, Rubén D. Martínez, Matthew C. Lamanna, Marcelo Luna, And Leonardo Salgado.

We describe Katepensaurus goicoecheai, gen. et sp. nov., a diplodocoid sauropod dinosaur from the Bajo Barreal Formation (Upper Cretaceous: Cenomanian–Turonian) of south-central Chubut Province, central Patagonia, Argentina. The holotypic specimen is a closely associated partial axial skeleton that includes cervical, dorsal, and caudal vertebrae. The dorsal vertebrae of Katepensaurus exhibit the following distinctive characters that we interpret as autapomorphies: (1) internal lamina divides lateral pneumatic fossa of centrum; (2) vertical ridges or crests present on lateral surface of vertebra, overlying neurocentral junction; (3) pair of laminae in parapophyseal centrodiapophyseal fossa; (4) transverse processes perforated by elliptical fenestrae; and (5) well-defined, rounded fossae on lateral aspect of postzygapophyses. Based on the results of previous phylogenetic analyses, we regard the new taxon as a member of Rebbachisauridae; more specifically, it may pertain to Limaysaurinae, a rebbachisaurid subclade that, to date, is definitively known only from southern South America. As currently understood, the rebbachisaurid fossil record suggests that the clade achieved its greatest taxonomic diversity within a few million years of its extinction during the early Late Cretaceous.

Ibiricu, L.M., Casal, G.A., Martínez, R.D., Lamanna, M.C., Luna, M. And Salgado, L. 2013. Katepensaurus goicoecheai, gen. et sp. nov., a Late Cretaceous Rebbachisaurid (Sauropoda, Diplodocoidea) from central Patagonia, Argentina. Journal of Vertebrate Paleontology 33(6):1351–1366.