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Suuwassea bone microstructure

From: Ben Creisler

A new online paper:

Brandon P. Hedrick, Allison R. Tumarkin-Deratzian, and Peter Dodson
Bone microstructure and relative age of the holotype specimen of the
diplodocoid sauropod dinosaur Suuwassea emilieae.
Acta Palaeontologica Polonica (in press)
doi: http://dx.doi.org/10.4202/app.2012.0049

We present the first study of bone microstructure in Suuwassea
emilieae, a diplodocoid sauropod from the Morrison Formation. Although
the holotype of Suuwassea was recently identified as a subadult, bone
histology demonstrates that this individual had reached sexual
maturity at approximately 75–80% of maximum adult size. The smaller
size of the holotype of Suuwassea relative to contemporary sauropods
is due to ontogeny rather than a true reflection of adult size. A
fully adult individual would have likely been similar in size to a
fully adult specimen of Apatosaurus. Suuwassea has a number of
plesiomorphic characters that might have been explained by its
supposed early ontogenetic status, and would then have called the
validity of the taxon into question. However, our demonstration that
it was an adult confirms that these features represent retention of
plesiomorphic character states or evolutionary reversals in a derived
animal. Additionally, the specimen shows extensive cortical drift and
secondary osteon formation related to skeletal loading, which is often
obscured by complete remodeling of Haversian systems in sauropod taxa.
There are substantial differences in the microstructure across the
bone, which could make histologic samples not based upon complete
cross sections problematic. Suuwassea is one of four currently
recognized dicraeosaurid taxa, and this study contributes potential
taxonomic characters in sauropod bone microstructure.