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Mussaurus (sauropodomorph) postcranial anatomy and phylogenetic relationships



From: Ben Creisler
bcreisler@gmail.com

In the new issue of JVP:

Alejandro Otero & Diego Pol (2013)
Postcranial anatomy and phylogenetic relationships of Mussaurus
patagonicus (Dinosauria, Sauropodomorpha)
Journal of Vertebrate Paleontology 33(5): 1138-1168
DOI:10.1080/02724634.2013.769444
http://www.tandfonline.com/doi/full/10.1080/02724634.2013.769444#.UidMqca1EYE

The transition from basal sauropodomorphs to sauropods is one of the
most dramatic evolutionary transformations in the history of
dinosaurs. Constituent taxa of this transition were recorded mainly in
South Africa and South America, and to a lesser extent in North
America. We describe here the postcranial anatomy of four specimens of
basal sauropodomorphs from the Late Triassic of Patagonia, Argentina,
and identify them as adult individuals of Mussaurus patagonicus. The
material is composed of one subadult and three adult specimens and was
originally identified as Plateosaurus. The completeness of the
material provides more complete knowledge of this taxon and allows us
to introduce aspects of basal sauropodomorph anatomy that were poorly
understood until now, such as the configuration and arrangement of the
distal carpal elements. The phylogenetic relationships of Mussaurus
patagonicus are tested through a cladistic analysis of basal
sauropodomorphs based on the anatomy of these specimens rather than on
the post-hatchling and juvenile specimens previously known for this
taxon. Mussaurus is recovered as a non-sauropod anchisaurian, being
the sister group of Aardonyx plus more derived sauropodomorphs and is
depicted outside the ‘quadrupedal clade,’ given the presence of
plesiomorphic features such as a humerus/femur ratio <0.8, a curved
femoral shaft in lateral view, and a nearly circular femoral midshaft
cross-section. Mussaurus patagonicus adds new and valuable information
that helps to clarify the core of the basal sauropodomorph-sauropod
transition.

SUPPLEMENTAL DATA—Supplemental materials are available for this
article for free at www.tandfonline.com/UJVP