Bone microstructure and developmental plasticity in birds and other dinosaurs
Article first published online: 26 SEP 2002
Copyright © 2002 Wiley-Liss, Inc.
Journal of Morphology
Volume 254, Issue 3, pages 232–246, December 2002
How to Cite
Starck, J. M. and Chinsamy, A. (2002), Bone microstructure and developmental plasticity in birds and other dinosaurs. J. Morphol., 254: 232–246. doi: 10.1002/jmor.10029
- Issue published online: 26 SEP 2002
- Article first published online: 26 SEP 2002
- South African–German agreement (National Research Foundation (NRF), South Africa and BMBF, Germany)
- German Research Council. Grant Number: STA 345/5-2
- bone histology;
- Cretaceous birds
Patterns of bone microstructure have frequently been used to deduce dynamics and processes of growth in extant and fossil tetrapods. Often, the various types of primary bone tissue have been associated with different bone deposition rates and more recently such deductions have extended to patterns observed in dinosaur bone microstructure. These previous studies are challenged by the findings of the current research, which integrates an experimental neontological approach and a paleontological comparison. We use tetracycline labeling and morphometry to study the variability of bone deposition rates in Japanese quail (Coturnix japonica) growing under different experimental conditions. We compare resulting patterns in bone microstructure with those found in fossil birds and other dinosaurs. We found that a single type of primary bone varies significantly in rates of growth in response to environmental conditions. Ranging between 10–50 μm per day, rates of growth overlap with the full range of bone deposition rates that were previously associated with different patterns of bone histology. Bone formation rate was significantly affected by environmental/experimental conditions, skeletal element, and age. In the quail, the experimental conditions did not result in formation of lines of arrested growth (LAGs). Because of the observed variation of bone deposition rates in response to variation in environmental conditions, we conclude that bone deposition rates measured in extant birds cannot simply be extrapolated to their fossil relatives. Additionally, we observe the variable incidence of LAGs and annuli among several dinosaur species, including fossil birds, extant sauropsids, as well as nonmammalian synapsids, and some extant mammals. This suggests that the ancestral condition of the response of bone to environmental conditions was variable. We propose that such developmental plasticity in modern birds may be reduced in association with the shortened developmental time during the later evolution of the ornithurine birds. J. Morphol. 254:232–246, 2002. © 2002 Wiley-Liss, Inc.