The core of the limb bone cortex of mammals and birds is made of rapidly deposited, fibro-lamellar bone tissue (also present in non-avian theropods), which is usually surrounded by an avascular outer circumferential layer (OCL) of slowly deposited parallel-fibered bone. We present the first comparative allometric study of the relative OCL thickness (expressed as a fraction of the diaphyseal radius) in modern birds. Body size explains 79% of the OCL variation in thickness, which is inversely correlated with size, that is, shows negative allometry (slope -0.799). This may explain the apparent absence of OCL in the ratites. Since the OCL is deposited at the end of growth, we propose that its relative thickness probably correlates with the amount of slow, residual growth, which our results suggest to be on the average larger in small birds.
How to translate text using browser tools
1 December 2004
Variation of the Outer Circumferential Layer in the Limb Bones of Birds
Fleur Ponton,
Andrzej Elżanowski,
Jacques Castanet,
Anusuya Chinsamy,
Emmanuel De Margerie,
Armand De Ricqlès,
Jorge Cubo
Acta Ornithologica
Vol. 39 • No. 2
December 2004
Vol. 39 • No. 2
December 2004
bone histology
ossification
periosteal bone
phylogenetically independent contrasts
postnatal growth
skeleton