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Dysalotosaurus bone histology
From: Ben Creisler
New in PLoS ONE:
Hübner, T.R. (2012)
Bone Histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia) –
Variation, Growth, and Implications.
PLoS ONE 7(1): e29958
Dysalotosaurus lettowvorbecki is a small ornithopod dinosaur known from
thousands of bones and several ontogenetic stages. It was found in a single
locality within the Tendaguru Formation of southeastern Tanzania, possibly
representing a single herd. Dysalotosaurus provides an excellent case study for
examining variation in bone microstructure and life history and helps to
unravel the still mysterious growth pattern of small ornithopods.
Five different skeletal elements were sampled, revealing microstructural
variation between individuals, skeletal elements, cross sectional units, and
ontogenetic stages. The bone wall consists of fibrolamellar bone with strong
variability in vascularization and development of growth cycles. Larger bones
with a high degree of utilization have high relative growth rates and seldom
annuli/LAGs, whereas small and less intensively used bones have lower growth
rates and a higher number of these resting lines. Due to the scarcity of
annuli/LAGs, the reconstruction of the life history of Dysalotosaurus was
carried out using regularly developed and alternating slow and fast growing
zones. Dysalotosaurus was a precocial dinosaur, which experienced sexual
maturity at ten years, had an indeterminate growth pattern, and maximum growth
rates comparable to a large kangaroo.
The variation in the bone histology of Dysalotosaurus demonstrates the
influence of size, utilization, and shape of bones on relative growth rates.
Annuli/LAGs are not the only type of annual growth cycles that can be used to
reconstruct the life history of fossil vertebrates, but the degree of developme
be of importance for the reconstruction of paleobehavior. The regular
development of annuli/LAGs in subadults and adults of large ornithopods
therefore reflects higher seasonal stress due to higher food demands,
migration, and altricial breeding behavior. Small ornithopods often lack
regularly developed annuli/LAGs due to lower food demands, no need for
migration, and precocial behavior.