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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.
Methodology/Principal Findings
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.