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Tehuelchesaurus osteology and phylogeny



From: Ben Creisler
bh480@scn.org

New paper:

JOSÉ L. CARBALLIDO, OLIVER W. M. RAUHUT, DIEGO POL and 
LEONARDO SALGADO (2011)
Osteology and phylogenetic relationships of 
Tehuelchesaurus benitezii (Dinosauria, Sauropoda) from 
the Upper Jurassic of Patagonia.
Zoological Journal of the Linnean Society (advance online 
publication)
DOI: 10.1111/j.1096-3642.2011.00723.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-
3642.2011.00723.x/abstract


The diversification and early evolution of neosauropod 
dinosaurs is mainly recorded from the Upper Jurassic of 
North America, Europe, and Africa. Our understanding of 
this evolutionary stage is far from complete, especially 
in the Southern Hemisphere. A partial skeleton of a large 
sauropod from the Upper Jurassic Cañadón Calcáreo 
Formation of Patagonia was originally described as 
a 'cetiosaurid' under the name Tehuelchesaurus benitezii. 
The specimen is here redescribed in detail and the 
evidence presented indicates that this taxon is indeed a 
neosauropod, thus representing one of the oldest records 
of this clade in South America. A complete preparation of 
the type specimen and detailed analysis of its osteology 
revealed a great number of features of phylogenetic 
significance, such as fully opisthocoelous dorsal 
vertebrae, the persistence of true pleurocoels up to the 
first sacral vertebra, associated with large camerae in 
the centrum and supraneural camerae, and an elaborate 
neural arch lamination, including two apomorphic laminae 
in the infradiapophyseal fossa. The phylogenetic 
relationships of this taxon are tested through an 
extensive cladistic analysis that recovers 
Tehuelchesaurus as a non-titanosauriform 
camarasauromorph, deeply nested within Neosauropoda. 
Camarasauromorph sauropods were widely distributed in the 
Late Jurassic, indicating a rapid evolution and 
diversification of the group.