From Yahoo: http://news.bbc.co.uk/2/hi/science/nature/5166518.stm
Bigger dinosaurs had warmer blood.
The bigger a dinosaur was, the warmer its blood, a study of the big beasts'
fossil remains shows.
[...]
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.