Rhoetosaurus, new anatomical information in new JVP

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com


In the new issue of Journal of Vertebrate Paleontology:

Jay P. Nair & Steven W. Salisbury (2012)
New anatomical information on Rhoetosaurus brownei Longman, 1926, a
gravisaurian sauropodomorph dinosaur from the Middle Jurassic of
Queensland, Australia.
Journal of Vertebrate Paleontology 32(2): 369-394
DOI:10.1080/02724634.2012.622324
http://www.tandfonline.com/doi/abs/10.1080/02724634.2012.622324



.Rhoetosaurus brownei is the only known named pre-Cretaceous sauropod
from Australia. It is therefore a potentially important taxon for
understanding global paleobiogeographic and phylogenetic patterns
among early sauropods. Despite its obvious significance, Rhoetosaurus
has been too poorly understood to be included in most recent analyses
of early sauropod evolution. With this in mind, we evaluated the
osteology and phylogeny of undescribed materials of Rhoetosaurus, in
order to attempt to close the gap in this understanding. The lower
hind limb of Rhoetosaurus highlights a plethora of differences from
other sauropods, supporting the distinctiveness of Rhoetosaurus even
in the absence of other materials. Some unique traits include
prominent crests and sulci on the tibia medially, a narrow metatarsal
articular bridge, and pedal claws with an accessory groove or fossa.
The pes plesiomorphically retains four claws where most sauropods have
three, and bears superficial similarity to that of Shunosaurus.
Preliminary cladistic analysis confirms that Rhoetosaurus is a
non-neosauropod gravisaurian, although weak support for the most
parsimonious topology suggests further findings are required to
improve upon incompleteness in the character data. Examination of
alternative phylogenetic hypotheses rules out a close relationship
between Rhoetosaurus and East Asian Jurassic sauropods, and indicates
a closer examination of the potential relationships between
Rhoetosaurus and other contemporaneous Middle Jurassic Gondwanan
sauropods is necessary.