Speculations on the growth rate and reproduction of some dinosaurs

Abstract

If the dinosaurs Protoceratops grangeri and Hypselosaurus sp. grew at rates predicted for their body size from extant reptiles, their expected ages at reproductive maturity would be about 20 and 62 yr respectively. This calculation assumes that dinosaurs grew at ectothermic rates which are about an order of magnitude slower than those of endothermic vertebrates of the same body size. Such delayed reproductive maturity may have set a premium on selection for high juvenile survivorship that is reflected in the relatively large eggs of these dinosaurs and in their only moderately large clutch sizes compared to modern reptiles.