Box 2 in Assessing dinosaur growth patterns: a microscopic revolution

Box 2. Assessing dinosaur longevity using the principle of Amprino's rule A less commonly utilized aging technique for dinosaurs and basal birds uses a principle called 'Amprino's rule' (sensu [11,22]). The formative rate of tissue types from living animals is used to estimate lengths of time for bone development and thus determine longevity. This aging technique is the only tested means to age animals in cases where growth lines were not deposited throughout life. The method has seen limited application in assessing dinosaur [11,22,31] and basal bird [11,36] longevity. In Figure Ia, the bones of an ostrich (Struthio camelus) were labeled by periodically administering fluorochromic chemical labels to establish the formative rate of the bone tissue (marked yellow and red; photo courtesy of Kristina Curry Rogers). Note that the values shown here are hypothetical and intended only to illustrate the methodology. The formation rate is divided into the amount of bone that formed during development (measured radially; Figure Ib) to reveal longevity.