History
Early attempts to estimate the longevity of dinosaurs used allometric scaling principles. Ages were determined by dividing individual mass estimates by rates of growth for similar, extant taxa. For very large individuals, growth rates were extrapolated to dinosaur proportions using regression analysis. The results of these investigations have been extremely variable as they depend on mass estimates and growth rates that are highly at odds with one another.
For example, longevity estimates for the sauropod Hypselosaurus priscus range from a few decades to several hundred years. Recently, however, it has been shown that most dinosaur bones have growth lines that are visible in thin sectioned material viewed under a polarized light source.
Read more about this topic: Age Determination In Dinosaurs
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