Bone microstructure and developmental plasticity in birds and other dinosaurs

Area of Science:

• Paleontology
• Comparative Anatomy
• Developmental Biology

Background:

• Bone microstructure analysis is crucial for understanding growth in extinct and extant tetrapods.
• Previous studies linked specific bone tissues to distinct deposition rates, including in dinosaur bone microstructure.

Purpose of the Study:

• To investigate the variability of bone deposition rates in Japanese quail under different experimental conditions.
• To compare these findings with bone microstructure patterns in fossil birds and dinosaurs.

Main Methods:

• Utilized tetracycline labeling and morphometry to study bone deposition rates in Japanese quail.
• Compared experimental results with paleontological data from fossil birds, dinosaurs, sauropsids, and mammals.

Main Results:

• A single type of primary bone exhibited significant growth rate variation (10-50 µm/day) in response to environmental conditions.
• Bone formation rate was influenced by experimental conditions, skeletal element, and age.
• Lines of arrested growth (LAGs) were not observed in quail under experimental conditions.

Conclusions:

• Bone deposition rates in extant birds cannot be directly extrapolated to fossil relatives due to environmental influences.
• The variable incidence of LAGs and annuli across diverse species suggests a historically plastic ancestral response to environmental conditions.
• Developmental plasticity in modern birds may have decreased with shortened developmental times in ornithurine bird evolution.