Growth Rings in Dinosaur Bones
Not all fossils preserve dramatic skeletons or sharp teeth. Some reveal microscopic structures that record patterns of growth. In many dinosaur bones, thin concentric lines appear when examined under magnification. These lines, known as growth rings, resemble those found in tree trunks and reflect periodic changes in bone deposition.
During favorable seasons, bone tissue forms rapidly. When environmental conditions become stressful—due to drought, cold, or limited resources—growth slows. The boundary between fast and slow deposition produces a visible ring. By counting these rings, researchers estimate an individual’s age at death.
Growth rings also provide insight into metabolism and life history. Closely spaced rings may indicate repeated stress events, while widely spaced rings suggest sustained growth. Comparisons across species show that some dinosaurs reached adult size quickly, supporting interpretations of relatively high metabolic rates.
Interpreting growth rings, however, requires caution. Not every line represents a full year, and disease or injury may interrupt normal deposition patterns. For this reason, paleontologists combine bone histology with other evidence such as body size, bone structure, and ecological context. When carefully analyzed, growth rings become valuable indicators of dinosaur development and environmental influence.
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(1) Which of the following best states the main idea of the passage?
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