Dr Cullen said: “Growth rate really varies, there’s no one size fits all.
“Birds have super growth spurts and reach adult size really fast, while reptiles like alligators and various lizards and snakes have extended growth.
“With them, a really, really big individual is probably old.”
By studying SUE’s fossilised bones, the researchers determined the dinosaurs’ growth patterns depend on their families.
The T-rex and its relative coelurosaurs hit massive growth spurts early on.
SUE, for example, lived to the ripe age of 33 and T-rexes most likely reached adult size by the time they were 20-years-old.