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Mesozoic marine reptiles: juvenile mosasauroids and ichthyosaur femurs
From: Ben Creisler
More marine reptiles stuff in new JVP:
Alexandra Houssaye & Paul Tafforeau (2012)
What vertebral microanatomy reveals about the ecology of juvenile
mosasaurs (Reptilia, Squamata).
Journal of Vertebrate Paleontology 32(5): 1042-1048
In mosasauroids, one of the major groups of Mesozoic marine reptiles,
various ecological grades have been identified. However, no data are
available concerning the ecology of the poorly known juveniles.
Osseous microanatomical organization appears to rely mainly on the
biomechanical constraints undergone by organisms. As such, it is
considered as a valuable paleoecological marker. The vertebral
microanatomy of several juvenile specimens of hydropelvic mosasauroids
(whose adult forms are active pelagic swimmers) was analyzed. This
study provides data about their growth mode and speed but, above all,
reveals that juvenile hydropelvic mosasauroids display microanatomical
features comparable to those of adults. This signifies that
hydropelvic mosasauroids were already highly efficient swimmers at a
very young age, contrary to plesiopelvic forms (i.e., those with a
terrestrial-like pelvis and limbs), that were relying on hydrostatic
(and not hydrodynamic) regulation of buoyancy and body trim. This
study tends to support recent views challenging the old hypothesis of
sheltered nurseries and shows that, in mosasauroids, the functional
requirements for buoyancy and body trim control are not correlated
with individual size.
Erin E. Maxwell, Maria Zammit & Patrick S. Druckenmiller (2012)
Morphology and orientation of the ichthyosaurian femur.
Journal of Vertebrate Paleontology 32(5): 1207--1211