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Mosasaur bone structure and growth rates



From: Ben Creisler
bh480@scn.org

Another new paper about mosasaurs:

ALEXANDRA HOUSSAYE & NATHALIE BARDET (2011)
Rib and vertebral micro-anatomical characteristics of hydropelvic
mosasauroids.
Lethaia (advance online publication)
DOI: 10.1111/j.1502-3931.2011.00273.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.2011.00273.x/abstract

Mosasauroids are squamates secondarily adapted to an aquatic life that
dominated the sea during the Late Cretaceous. Mosasauroids display distinct
types of morphologies illustrating steps in the adaptation of this lineage
to increasing obligatory habits. Hydropelvic mosasauroids (sensu Caldwell &
Palci) were the most highly adapted to an open-sea environment. Contrary to
plesiopelvic forms, they are considered to have relied on a hydrodynamic,
rather than hydrostatic buoyancy and body trim control strategies. This led
previous authors to consider that these taxa would favour bone lightening
(osteoporotic-like condition) rather than bone mass increase. Although an
osteoporotic-like state was indeed described in Clidastes and Tylosaurus,
bone mass increase was reported in Platecarpus. As a matter of fact, the
new analysis of vertebral thin sections of various taxa combined with the
reanalysis of the rib sections available in Sheldon?s PhD thesis in a
micro-anatomical perspective reveals the absence of both bone mass increase
and bone lightening in these organisms. These taxa in fact display a
vertebral micro-anatomy much peculiar within squamates. It
characteristically corresponds to a true network of thin trabeculae whose
tightness varies between taxa, probably as a result of both species and
individual size differences, particularly the latter. In addition, analysis
of the pattern of vascularization as observed in hydropelvic mosasauroids,
which is unique amongst squamates, suggests that large size in hydropelvic
mosasauroids would mainly rely on protracted rather than faster growth
rates. 


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