Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina

Background: Living birds possess a unique heterogeneous pulmonary system composed of a rigid, dorsally-anchored lung and several compliant air sacs that operate as bellows, driving inspired air through the lung. Evidence from the fossil record for the origin and evolution of this system is extremely limited, because lungs do not fossilize and because the bellow-like air sacs in living birds only rarely penetrate (pneumatize) skeletal bone and thus leave a record of their presence. Methodology/Principal Findings: We describe a new predatory dinosaur from Upper Cretaceous rocks in Argentina, Aerosteon riocoloradensis gen. et sp. nov., that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium. In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation. We also describe several pneumatized gastralia (‘‘stomach ribs’’), which suggest that diverticulae of the air sac system were present in surface tissues of the thorax. Conclusions/Significance: We present a four-phase model for the evolution of avian air sacs and costosternal-driven lung ventilation based on the known fossil record of theropod dinosaurs and osteological correlates in extant birds: (1) Phase I—Elaboration of paraxial cervical air sacs in basal theropods no later than the earliest Late Triassic. (2) Phase II—Differentiation of avian ventilatory air sacs, including both cranial (clavicular air sac) and caudal (abdominal air sac) divisions, in basal tetanurans during the Jurassic. A heterogeneous respiratory tract wit

A Provenance Analysis from the Lower Jurassic Units of the Neuquén Basin. Volcanic Arc or Intraplate Magmatic Input?

A possible signal of the Jurassic Chon Aike Igneous Province within the early infill of the Neuquén Basin is recognized in our provenance analyses. We use a combination of detrital zircon geochronology and Lu-Hf isotope analysis, along with sandstone petrography descriptions to characterize the sediments source region in the Cuyo Group. The sandstone petrographic analysis confirms important contributions from volcanic sources of different compositions. U-Pb ages and Hf isotopes obtained in the analyzed zircons indicate a more complex configuration given by multiple igneous components. The variations in the provenance patterns allow us to make some observations about the paleogeographic evolution of the basin. At the base of the sequence, the sediments were derived from local sources composed of Permian basement and Upper Triassic volcanic rocks, whereas in the top, the zircons were supplied from Lower Jurassic volcanic rocks and Lower Paleozoic and Precambrian basements suggesting more distal and ancient sources. Low values of εHft (-15.5 to -0.7) analyzed in Permian and Triassic detrital zircons indicated an evolved source with strong crustal contribution. This data is in agreement with the negative values of εHft and εHft calculated in Permian and Triassic igneous rocks from the North Patagonian Massif. The Hft about -4 of the Jurassic detrital zircons indicated a crustal origin for the source rocks and are clearly compatible with the isotopic compositions of the Chon Aike Igneous Province. A volcanic source region compatible with the Andean arc is dismissed because the Jurassic arc has isotope characteristics of a mantle source.Fil: Naipauer, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Garcia Morabito, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Manassero, Marcelo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Valencia, Victor. University of Washington; Estados UnidosFil: Ramos, Victor Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin

Landscapes and Geology of Patagonia: An Introduction to the Land of Reptiles

The purpose of this chapter is to summarize the geological-geomorphologicalregions of Patagonia with a general characterization of the maingeomorphological units. A review of studies on geology, stratigraphic, main geologiclandmarks, geological history, and geological resources will be brieflydescribed. This review was performed on the base of geological province concept,including a stratigraphic-morphostructural criteria and a description of majorendogenous and exogenous processes responsible for the formation of landscapeunits. In this chapter these geological-geomorphological regions include Chile andArgentina and were grouped as: (1) Coastal Cordillera and Central Valley (Chile),(2) Southern Andes Cordillera, (3) Mountain Sector of the Neuquén Embayment,(4) Northern Patagonian Tablelands, (5) The North Patagonian Broken Foreland andSomún Curá Massif, (6) Central Patagonian Tablelands, (7) Deseado Massif, (8)Southern Patagonian Tableland, and (9) Islas Malvinas Plateau.Fil: Bouza, Pablo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; ArgentinaFil: Bilmes, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentin

Orbital controls and high-resolution cyclostratigraphy of Late Jurassic Early-Cretaceous in the Neuquén Basin

Detailed cyclostratigraphic analyses have been made from seven Tithonian–Hauterivian sections of the Vaca Muerta and Agrio Formations, exposed in southern Mendoza area of the Neuquén Basin. Both lithostratigraphic units are characterized by decimeter-scale rhythmic alternations of marlstones and limestones, showing a well-ordered hierarchy of cycles, including elementary cycles, bundles, and superbundles. According to biostratigraphic data, elementary cycles have a periodicity of ~18–21 ky, which correlates with the precessional cycle of the Earth’s axis. Spectral analysis based on time series of elementary cycle thicknesses allowed us to identify frequencies of ~400 ky, and ~90–120 ky, which we interpret as the modulation of the precessional cycle by the Earth’s orbital eccentricity. A third band frequency of ~40 ky was also identified that can be assigned to the obliquity cycle. Cyclostratigraphy enabled the construction of almost continuous floating astronomical time scale for the Tithonian–Hauterivian, for which a minimum duration of 5.67 myr for the Tithonian, 5.27 myr for the Berriasian, >3.45 myr for the Valanginian, and 5.96 myr for the Hauterivian have been assessed. Additionally, the likely transference mechanisms of the orbital signal to the sedimentary record are analyzed, proposing the coexistence of carbonate exportation and dilution as the dominant mechanisms.Fil: Kietzmann, Diego Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Iglesia Llanos, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Kohan Martinez, Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin