sentences:  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 per year during the rapid growth phase, slower than in tyrannosaurines like "Daspletosaurus" and "Tyrannosaurus", but comparable to "Albertosaurus".