The word “cold-blooded” is rather scientifically vague, today we use terms such as poikilothermy or ectothermy in which body temperature is expected to fluctuate and is controlled by external means. Homeothermy and endothermy refer to “warm-blooded” animals, which regulate their temperature with the use of thermal homeostasis internally. Previously, it was widely believed that dinosaurs were ectotherms, similar to lizards of today but now it is believed that many could have been endotherms similar to modern day mammals.
Temperature records illustrate alternating warm and cool periods over millions of years. These suggest that during the Jurassic, Triassic and Cretaceous periods the climate was relatively warm through out. This could be evidence for the theory that all dinosaurs were ectotherms. Because of the steady temperatures that occurred throughout this period ectothermic animals would have flourished in this environment. Ectotherms could have maintained a relatively stable core body temperature because temperatures were not likely to fluctuate greatly; some biologists suggest that the smaller dinosaurs had body temperatures close to 25ºC – which is the expected average temperature of that time. With this constant environmental temperature there would be no need to regulate their temperatures internally, also if the conditions were often dry and arid then food and water may have been in short supply, this would have meant that mammalian like creatures could not have had obtained enough food for their high metabolic rates, whereas reptiles can tolerate ranges in temperature and are able to maintain water. But temperatures must have fluctuated seasonally so this would suggest a need for thermoregulation during the very cold or very hot months.
Evidence of dinosaur fossils at the poles could suggest endothermy in dinosaurs, although the climate would have been much warmer and forest was expected to reach towards the poles in the absence of ice caps, because of the Earths tilt this area would still experience long periods of cold and dark. Signifying that the dinosaurs must have had some sort of thermoregulatory system to survive the winter, but this could also be evidence for a migration because the pole areas would have flourished during the summer, so dinosaurs may have migrated during the 6 cold months of the year. Other theories such as the reason for the mass extinction of dinosaurs could have been that at the end of the cretaceous period temperatures dropped dramatically and there was increased variation across the Earth, this could have meant that ectothermic dinosaurs would have struggled to survive and regulate their temperature and therefore perish.
The evidence of growth rings on dinosaur teeth is valuable when suggesting whether the dinosaur was endothermic or ectothermic. Growth rings are attributed to the inability of ectotherms to maintain high levels of activity, feeding and growth during months in which food is sparse and temperatures are at extremes. Because endotherms can maintain a constant body temperature seasonal growth rings do not appear. The discovery of dinosaur teeth from Alberta Canada include that of Saurischia, Ornischia and Ceratopsidae from the late Cretaceous period. They show similarities to that of modern day crocodilians, affected by seasonal variations. The rings demonstrate periodicity of growth, when there is a narrow hypercalcified band this means a hard winter in which productivity was low and the dinosaur struggled to maintain a constant temperature and other bodily functions. Because of the similarities between crocodiles and dinosaurs of this area, this would suggest similar thermal physiologies, thus implying that these dinosaurs were ectotherms.
Using growth rate, mass of dinosaur, environmental temperature and productivity, temperature of dinosaur can be predicted. Results suggest that larger dinosaurs had higher constant body temperatures which could be evidence for endothermy. But other theories suggest that large dinosaurs maintained their temperature using thermal inertia. Dinosaur body temperatures change over the ontogeny of an individual, body temperatures increased by less than 3ºC over ontogeny for a species reaching 300kg but more than 20ºC for a species reaching 25000kg. This relative change in body temperature is similar to observed increase in temperature for extant crocodiles. The model suggests that larger dinosaurs were able to maintain a constant temperature because they were so big and not because they had thermoregulation. Soft tissue of Theropod dinosaurs suggests that they may have had unmodified septate lungs, ventilated with the assistance of an active hepatic piston-diaphragm mechanism. The presence of this mechanism could be the answer to why dinosaurs maintained a routine metabolic rate like ectotherms but still managed to sustain active oxygen consumption rates and activity levels beyond living reptiles.
Other evidence for endothermy is need for high arterial pressures particularly in large dinosaurs. In dinosaurs such as the brachiosaurus reaching heights of 25 meters high arterial pressures must have been essential, because of its large vertical distance from heart to head it would have required a 6.5meter blood column producing pressures of 500m
mHg to provide adequate exchange of metabolites. No reptiles of today show such large heart to head ratios and are often low lying animals, these dinosaurs may have bowed their heads but skeletal structure suggests it remained in fairly up right position. If these large animals were aquatic then this would have suggested that the pressure needed for the blood column would have been equalized by hydrostatic pressure. Pterosaurs, like birds possessed an insulating cover of hair like structures similar to feathers this would suggest a need of insulation and therefore an endothermic animal. A lot of other dinosaurs did not posses this so could be considered as ectotherms. Histologically dinosaur bone is neither like that of endotherms or ectotherms but in some dinosaurs primary bone shows fibro-lamella bone deposited in zones separated by lines of arrested growth. This fairly slow growth punctuated by slow or even ceased growth is evidence of seasonal alterations between fast and slow rates of bone deposition. There is little evidence for this kind of growth in endotherms today however some dinosaurs such as the small ornithopod have azonal fibro-lamella suggesting continuous growth.
mHg to provide adequate exchange of metabolites. No reptiles of today show such large heart to head ratios and are often low lying animals, these dinosaurs may have bowed their heads but skeletal structure suggests it remained in fairly up right position. If these large animals were aquatic then this would have suggested that the pressure needed for the blood column would have been equalized by hydrostatic pressure. Pterosaurs, like birds possessed an insulating cover of hair like structures similar to feathers this would suggest a need of insulation and therefore an endothermic animal. A lot of other dinosaurs did not posses this so could be considered as ectotherms. Histologically dinosaur bone is neither like that of endotherms or ectotherms but in some dinosaurs primary bone shows fibro-lamella bone deposited in zones separated by lines of arrested growth. This fairly slow growth punctuated by slow or even ceased growth is evidence of seasonal alterations between fast and slow rates of bone deposition. There is little evidence for this kind of growth in endotherms today however some dinosaurs such as the small ornithopod have azonal fibro-lamella suggesting continuous growth.
For many years dinosaurs have been considered as being slow moving animals, especially large dinosaurs as rapid gaits would have been impossible because of their sheer size this is similar to modern day elephants who are relatively slow movers so absolute speed does not increase with body size. Other evidence suggests that their physiology simply would not allow it. The position of the dinosaur scapula in relation to the vertical humerus is also maximally protracted position for the scapilohumeral complex, further protraction of glenoid would have resulted in impossible positions. Also further reach of the vertebrate could have only been accomplished by flexing fore limb and elbow and for a heavy animal this would create sheer forces which would ultimately increase with speed. This shows that in some dinosaurs such as the triceratops reaching high speeds would have been impossible. Other ideas on dinosaur locomotion suggest that certain dinosaurs would not have enough knee extensor muscles to run slowly and hip extensor muscles would not have been able to sustain high speeds.
Although dinosaur morphology has suggested that many of them were slow moving new evidence from track sites states that some species could be fast moving. Previous trackway sites in British Columbia and Queensland state that many of the trails show slow moving animals. In Texas a new trackway site has been used to estimate the speed of the dinosaurian trail maker from the size of its foot prints 
and stride. Here some species of dinosaur appear to be reaching speeds of 22msֿ¹ much faster than previous evidence. Although this evidence doesn’t categorically prove the speeds of these dinosaurs it states that either these were the speeds they were traveling or they had unusually long legs. It’s also worth noting that in these investigations it was largely found to be a smaller species that was fast moving and that in fact speed decreased as the animals size increased.
When looking at creatures that lived millions of years ago it is difficult to determine intelligence with only skeletal structures and a few soft tissues as evidence. But one method used in determining the complexity of neural development is comparing brain size of a particular animal to that expected of an animal of that size. By using endocasts developed from dinosaur skulls brain size and size of brain sections can be determined or at least estimated. Brain size and therfore intellect is important in predicting behavior of dinosaurs, for example sense of smell and foraging ability or predation skills. 
and stride. Here some species of dinosaur appear to be reaching speeds of 22msֿ¹ much faster than previous evidence. Although this evidence doesn’t categorically prove the speeds of these dinosaurs it states that either these were the speeds they were traveling or they had unusually long legs. It’s also worth noting that in these investigations it was largely found to be a smaller species that was fast moving and that in fact speed decreased as the animals size increased.
When exploring the neurology of a dinosaur it is difficult to make a measure of intelligence, for example just using brain size isn’t enough as a larger brain size could imply better eyesight but not necessarily increased intelligence. Dinosaurs are thought to have had some of the smallest brains for their body size of any vertebrates with the view that they could only produce simple behaviors but if you compare the brain size of the animal to that of an expected brain size for an animal of that size dinosaurs fall well within the expected range for their body size. Soft tissue structure or imprints can be retained inside the skulls of dinosaurs, taking endocasts of these skulls enables us to interpret brain size and function. The large Sauropod dinosaurs had comparatively small brains for their size but this could have been influenced by adaptive requirements of head size and weight so far from ground so is not used in the relationship between brain and body size. An equation was used to estimate intelligence which was the size of dinosaur divided by the size of brain of an animal of that size, known as EQ the lower the EQ the less complex its brain. Dinosaurs such as the stegosaurus had low a low EQ and this can be confirmed by its limb structure which suggests a lack of agility and speed which was not essential it also had defensive weapons on its tail suggesting a passive defence. Theropods were found to have larger brains and therefore higher EQs which is understandable as they were mostly carnivores and would have required a more complex neurology to hunt with 
an agile, lightly built physique and grasping fore limbs.
an agile, lightly built physique and grasping fore limbs.
Other evidence is obtained from the similarities of neurological features in dinosaurs and animals from today. The caiman endocasts and alligator brain exhibit notable similarity with A.fragilis endocasts. In the A.fragilis endocasts there are well defined structures of vestibular sense organs with distinct similarities to the alligators vestibular apparatus not shared with turtles, iguanas or birds. Behavior can be proposed based on modern day reptiles, substantial elaboration of cerebrum imparts greater neuronal complexity enabling organisms to extend foraging ability.
In conclusion, Dinosaurs were pretty awesome. Ok, so they won't loose their name...- from the greek 'potent lizard' but I hope you're now inspired to find out more about these varied creatures as I have only touched on there facinating physiology and behaviour. So what were Dinosaurs? Not just over-sised lizards thats for sure....
