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Osteology of Rebbachisaurus, diplodocoid sauropod from Late Cretaceous of Morocco



Ben Creisler
bcreisler@gmail.com

A new online paper:

Jeffrey A. Wilson & Ronan Allain (2015)
Osteology of Rebbachisaurus garasbae Lavocat, 1954, a diplodocoid
(Dinosauria, Sauropoda) from the early Late Cretaceous–aged Kem Kem
beds of southeastern Morocco.
Journal of Vertebrate Paleontology (advance online publication)
DOI:10.1080/02724634.2014.1000701
http://www.tandfonline.com/doi/full/10.1080/02724634.2014.1000701

The holotype of the sauropod dinosaur Rebbachisaurus garasbae was
discovered in infra-upper Cenomanian horizons of the Kem Kem region of
southeastern Morocco in the 1940s and 1950s. The original materials
included part of a vertebral column, some of which was found in
articulation, and a scapula, a humerus, and an ischium. Of these
remains, only the scapula and one of the dorsal vertebrae have been
described, but in abbreviated form. Following complete preparation of
the partial skeleton, careful examination and fitting of scores of
fragments collected with these materials, and computed tomography
imaging of the most complete vertebra, we present a complete
description of the holotype of Rebbachisaurus garasbae. Our
description identifies several autapomorphies of the dorsal and caudal
vertebrae, both relating to the shape of the vertebrae and the
architecture of their laminae. Based on our reassessment of its
anatomy, Rebbachisaurus is recovered as a member of an Afro-European
clade that includes Nigersaurus and Demandasaurus. Due to the large
size of one of its dorsal vertebrae (ca. 1.45 m tall), Rebbachisaurus
has been considered to be a large sauropod. The size of the vertebral
centra and the length and cross-sectional area of the humerus of
Rebbachisaurus, however, indicate this individual weighed 7915–12,015
kg, which is slightly larger than Amargasaurus but comparable in size
to some individuals of Dicraeosaurus. The dorsal vertebrae of
Rebbachisaurus and other rebbachisaurids have been suggested to be
highly mobile, but results suggest that anatomical features of the
vertebrae actually limited rotation and increased resistance to
dorsoventrally directed forces applied to the transverse processes.