Sauropod dinosaurs include the largest terrestrial animals and are considered to have uninterrupted rapid rates of growth, which differs from their more basal relatives, which have a slower cyclical growth. Here we examine the bone microstructure of several sauropodomorph dinosaurs, including basal taxa, as well as the more derived sauropods. Although our results agree that the plesiomorphic condition for Sauropodomorpha is cyclical growth dynamics, we found that the hypothesized dichotomy between the growth patterns of basal and more derived sauropodomorphs is not supported. Here, we show that sauropod-like growth dynamics of uninterrupted rapid growth also occurred in some basal sauropodomorphs, and that some basal sauropods retained the plesiomorphic cyclical growth patterns. Among the sauropodomorpha it appears that the basal taxa exploited different growth strategies, but the more derived Eusauropoda successfully utilized rapid, uninterrupted growth strategies.
Two end-member models have been proposed for the Paleogene Andean foreland: a simple W-E migrating foreland model and a broken-foreland model. We present new stratigraphic, sedimentological and structural data from the Paleogene Quebrada de los Colorados (QLC) Formation, in the Eastern Cordillera, with which to test these two different models. Basin-wide unconformities, growthstrata and changes in provenance indicate deposition of the QLC Formation in a tectonically active basin. Both west-and east-vergent structures, rooted in the basement, controlled the deposition and distribution of the QLC Formation from the Middle Eocene to the Early Miocene. The provenance analysis indicates that the main source areas were basement blocks, like the Paleozoic Oire Eruptive Complex, uplifted during Paleogene shortening, and that delimits the eastern boundary of the present-day intraorogenic Puna plateau. A comparison of the QLC sedimentary basin-fill pattern with those of adjacent Paleogene basins in the Puna plateau and in the Santa B arbara System highlights the presence of discrete depozones. These reflect the early compartmentalization of the foreland, rather than a stepwise advance of the deformation front of a thrust belt. The early Tertiary foreland of the southern central Andes is represented by a ca. 250-km-wide area comprising several deformation zones (Arizaro, Mac on, Copalayo and Calchaqu ı) in which doubly vergent or asymmetric structures, rooted in the basement, were generated. Hence, classical foreland model is difficult to apply in this Paleogene basin; and our data and interpretation agree with a broken-foreland model.
Birds are unique among living tetrapods in possessing pneumaticity of the postcranial skeleton, with invasion of bone by the lung and air-sac system. Postcranial skeletal pneumaticity (PSP) has been reported in numerous extinct archosaurs including pterosaurs and nonavian dinosaurs. Here we report a case of extreme PSP in a group of small-bodied, armored sauropod dinosaurs from the Upper Cretaceous of South America. Based on osteological data, we report an extensive invasion of pneumatic diverticula along the vertebral column, reaching the distal portion of the tail. Also, we provide evidence of pneumaticity in both pectoral and pelvic girdles. Our study reveals that the extreme PSP in archosaurs is not restricted to pterosaurs and theropod dinosaurs. Keywords Sauropoda Á Titanosauria Á Upper Cretaceous Á Air-sac system Á Appendicular pneumaticity Kurzfassung Vögel sind einzigartig innerhalb der lebenden Tetrapoden, da sie eine Pneumatisierung des Postkranialskeletts aufweisen, welche die Invasion von Knochen durch die Lunge und Luftsack-Systeme einschließt. Diese postkraniale Skelettpneumatisierung (PSP) ist bereits in zahlreichen ausgestorbenen Archosauriern, einschließlich Pterosauriern und Dinosauriern, die nicht der Vogellinie angehören, beschrieben worden. Hier berichten wir über einen Fall von extremer PSP in einer Gruppe von kleinwüchsigen, gepanzerten sauropoden Dinosauriern aus der Oberkreide von Südamerika. Basierend auf osteologischen Daten lässt sich eine umfangreiche Invasion von pneumatischen Divertikeln entlang der Wirbelsäule nachweisen, welche sich bis in die distalen Bereiche des Schwanzes erstreckt. Darüber hinaus zeigen sich Hinweise auf Pneumatisierung in beiden Brust-und Beckengürteln. Unsere Studie zeigt, dass diese extreme Form von PSP in Archosauriern nicht auf Flugsaurier und theropode Dinosaurier beschränkt ist.
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