Megan Cassidy, of Leithfield School, asks :-

Were any dinosaurs warm blooded?

Richard Holdaway, a biologist in private practice in Christchurch, responded.

Unfortunately Megan there is no agreed answer as to whether dinosaurs were warm-blooded or cold-blooded. It is very likely that some groups could produce their own body heat, and that others either used heat from the sun or a combination of methods to gain enough heat to be active.

In favour of endothermy (which means warm-blooded) are: rapid growth in body size for some groups; detailed structure of the bone (warm-blooded animals have more blood vessels in their bones than do cold-blooded animals such as lizards - dinosaur bones had lots of blood vessels); the fast pace of some dinosaurs as shown by studies of their tracks; their upright posture, which takes more energy than a reptilian sprawl; the fact that some of them lived in seasonally cold climates and may have migrated; and the way birds work today, because birds evolved from a group of predatory dinosaurs and therefore must have inherited their body functions.

Most arguments against warm-bloodedness are negative: dinosaurs could have worked without being warm-blooded; bone structure could mean other things; they could have used the sun's warmth, etc. Dinosaurs lived on Earth for 135 million years. It is very likely that some did develop the ability to produce their own body heat, and that earlier ones had less involved body systems, just as today some mammals, such as marsupials, have lower body temperatures than others.