There are two different kinds of metabolisms
we ascribe to animals today, warm-blooded like us humans are creatures that control their
body temperatures, body temperatures tend to be warm, we're at ninety eight point six and our body temperature doesn't vary,
unless we're sick, it doesn't vary with the outside
temperature. Lizards, and a lot of other kinds of
animals, of course, are what we call cold-blooded, not really cold-blooded technically, but what that
means is their body temperatures, internal body
temperature is much more labile, much more sensitive to the environment, when it's cold outside, their body temperature is cold, when it's hot their body temperature warms up. What
were dinosaurs? Well we don't really know the answer to that question, actually based on some of the evidence
of posture and locomotion we actually think that some of these more predatory
dinosaurs might've been warm-blooded, whereas some of the larger
vegetarian animals might have been cold-blooded, but we don't know that directly. But one thing is certain, that birds are warm-blooded animals and
birds are a kind of dinosaur so somewhere in the evolution of
dinosaurs warm-bloodedness eveolved. Maybe in those
dinosaurs that aren't strictly classified as birds, maybe Tyrannosaurus was warm-blooded, we don't know that for
sure but it's a good supposition.