 Bibliography and Index of the Sirenia and Desmostylia 
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Houssaye, Alexandra; Waskow, Katja; Hayashi, Shoji; Cornette, Raphaël; Lee, Andrew H.; Hutchinson, John R.
(detail)
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2015 |
Biomechanical evolution of solid bones in large animals: a microanatomical investigation.
Biol. Jour. Linn. Soc. 117(2): 350-371. 6 tabs. 7 figs. DOI:10.111/bij.12660 Feb. 2016 (publ. online Sept. 8, 2015).
–Graviportal taxa show an allometric increase of the cross-sectional area of supportive bones and are assumed to display microanatomical changes associated with an increase in bone mass. This evokes osteosclerosis (i.e. an increase in bone compactness observed in some aquatic amniotes). The present study investigates the changes in bones' microanatomical organization associated with graviportality and how comparable they are with aquatically acquired osteosclerosis aiming to better understand the adaptation of bone to the different associated functional requirements. Bones of graviportal taxa show microanatomical changes that are not solely attributable to allometry. They display a thicker cortex and a proportionally smaller medullary cavity, with a wider transition zone between these domains. This inner cancellous structure may enable to better enhance energy absorption and marrow support. Moreover, the cross-sectional geometric parameters indicate increased resistance to stresses engendered by bending and torsion, as well as compression. Adaptation to a graviportal posture should be taken into consideration when analyzing possibly amphibious taxa with a terrestrial-like morphology. This is particularly important for palaeoecological inferences about large extinct tetrapods that might have been amphibious and, more generally, for the study of early stages of adaptation to an aquatic life in amniotes.
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Daryl P. Domning, Research Associate, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, and Laboratory of Evolutionary Biology, Department of Anatomy, College of Medicine, Howard University, Washington, D.C. 20059.
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