 Gregory Erickson and colleagues have studied the growth and life history of tyrannosaurids using bone histology , which can determine the age of a specimen when it died . A growth curve can be developed when the ages of various individuals are plotted against their sizes on a graph . Tyrannosaurids grew throughout their lives , but underwent tremendous growth spurts for about four years , after an extended juvenile phase . Sexual maturity may have ended this rapid growth phase , after which growth slowed down considerably in adult animals . Examining five Gorgosaurus specimens of various sizes , Erickson calculated a maximum growth rate of about 50 kg ( 110 lb ) per year during the rapid growth phase , slower than in tyrannosaurines like Daspletosaurus and Tyrannosaurus , but comparable to Albertosaurus . 
