Friday, September 5, 2014

[Paleontology • 2014] Dreadnoughtus schrani • A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina


Dreadnoughtus schrani 
Lacovara, Lamanna, Ibiricu, Poole, Schroeter, Ullmann, Voegele, Boles, Carter, Fowler, Egerton, Moyer, Coughenour, Schein, Harris, Martínez & Novas, 2014 | doi: 10.1038/srep06196

Titanosaurian sauropod dinosaurs were the most diverse and abundant large-bodied herbivores in the southern continents during the final 30 million years of the Mesozoic Era. Several titanosaur species are regarded as the most massive land-living animals yet discovered; nevertheless, nearly all of these giant titanosaurs are known only from very incomplete fossils, hindering a detailed understanding of their anatomy. Here we describe a new and gigantic titanosaur, Dreadnoughtus schrani, from Upper Cretaceous sediments in southern Patagonia, Argentina. Represented by approximately 70% of the postcranial skeleton, plus craniodental remains, Dreadnoughtus is the most complete giant titanosaur yet discovered, and provides new insight into the morphology and evolutionary history of these colossal animals. Furthermore, despite its estimated mass of about 59.3 metric tons, the bone histology of the Dreadnoughtus type specimen reveals that this individual was still growing at the time of death.



Figure 2: Reconstruction, appendicular skeletal anatomy, and bone histology of Dreadnoughtus schrani.
(A) Reconstructed skeleton and body silhouette in left lateral view with preserved elements in white. (B) Left scapula and coracoid in lateral view. (C) Sternal plates in ventral view. (D) Left forelimb (metacarpus reconstructed) in anterior view. (E) Left pelvis (ilium partially reconstructed) in lateral view. (F) Left hind limb in anterior view (metatarsus and pes partially reconstructed and reversed from right). (G) Transverse ground thin section of humeral shaft, showing heavy secondary remodelling (arrow indicates extent of dense osteon formation), a thick layer of well-vascularized fibrolamellar bone, and a lack of lines of arrested growth or an external fundamental system.

Systematic Palaeontology
Dinosauria Owen 1842. Saurischia Seeley 1887.
 Sauropoda Marsh 1878. Titanosauriformes Salgado, Coria, and Calvo 1997.
Titanosauria Bonaparte and Coria 1993.
Dreadnoughtus schrani nov. gen. nov. sp.

Etymology
Dreadnought (Old English), fearing nothing; genus name alludes to the gigantic body size of the taxon (which presumably rendered healthy adult individuals nearly impervious to attack) and the predominant battleships of the early 20th century (two of which, ARA [Armada de la República Argentina] Rivadavia and ARA Moreno, were part of the Argentinean navy). Species name honours the American entrepreneur Adam Schran for his support of this research. 

Figure 3: Time-calibrated hypothesis of phylogenetic relationships of Dreadnoughtus schrani (Consistency Index = 0.42, Retention Index = 0.76, Rescaled Consistency Index = 0.32) with relevant clades labelled.




Kenneth J. Lacovara, Matthew C. Lamanna, Lucio M. Ibiricu, Jason C. Poole, Elena R. Schroeter, Paul V. Ullmann, Kristyn K. Voegele, Zachary M. Boles, Aja M. Carter, Emma K. Fowler, Victoria M. Egerton, Alison E. Moyer, Christopher L. Coughenour, Jason P. Schein, Jerald D. Harris, Rubén D. Martínez and Fernando E. Novas. 2014. A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina. Scientific Reports. doi: dx.doi.org/10.1038/srep06196

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