T. rex
Dinosaurs were long considered to be cold-blooded reptiles.
an equation showing the relationship between body size, body temperature and growth rate of an animal.
They then applied this equation, which has been shown to be valid across a variety of living species, to dinosaurs.
the smallest dinosaurs had temperatures of around 25C, close to environmental temperatures and similar to those observed for living reptiles.
they did not actively regulate their internal temperature like mammals and birds.
But as dinosaurs got bigger, they became less efficient at dissipating heat and this helped to keep them warm anyway. This is known as inertial homeothermy.
According to the scientists' equation
the enormous sauropod Apatosaurus - which at 13,000kg was among one of the biggest dinosaurs - had a body temperature of just over 40C
Most animals cannot tolerate body temperatures of above 45C
the maximum size a dinosaur could grow to was limited by body temperature.