1) Palaeontologists are interested in whether dinosaurs were warm or cold blooded (ie did they have a mammalian or reptilian metabolism?) Mammals and birds have regulating mechanisms which maintain their core body temperatures at a steady value day and night so they are classified as endotherms. Modem reptiles do not have this ability to regulate their body temperature; they are ectotherms. When resting their temperature depends on their surroundings so in cool conditions their body temperature tends to fall (and vice-versa).