Not in cold blood - news story - 28 Jun 2012
Getting warmer
The logical assumption, when it was realised dinosaurs were reptilian, was that they had cold blood. Gradually, it dawned on palaeontologists that this wasn't necessarily true and, furthermore, looking less and less likely the more we found out. It's generally accpeted these days that dinosaurs were probably warm-blooded.
Growth rings in bones show periods of lessened growth - times of the year when the animal wasn't getting any bigger. Dinosaur bones show these markings clearly, as do those of modern reptiles. This link was originally used as evidence dinosaurs were cold-blooded. However, recent research shows that mammalian bones also show these patterns, removing any link between bone growth rings and the animals body temperature regulation methods.
The growth patterns can still tell us something about the animal, though. As with trees, periods of difficult environmental conditions or low food supply can be indicated by spells of poor development. You can read more by clicking here.