Also, the climate in the Mesozoic was generally warmer and milder than today (we're just recovering from the last ice age, remember). Even if they were somewhat cold, dinosaurs could have migrated there in the summer when it was warmer, and emmigrated during the cooler winter. Problem: The high latitudes (Alaska, Antarctica, etc.) that dinosaur fossils have been found at were not so cold in the Mesozoic in fact they may have been almost sub-tropical. Hypothesis: Dinosaur fossils are known from high latitudes, so they must have been endothermic to cope with the cold. Given: Ectotherms are not normally found at high latitudes (it's cold). Many dinosaurs had quite typical reptile-sized brains. Not an empirically supported 'if.then' relationship.Also, the data on dinosaur brain size is scant at best being measured from the few complete skulls available. Problem: Large brain size may be correlated with endothermy, but it is correlated with many other features not necessarily related to endothermy. Hypothesis: Theropod and ornithopod dinosaurs had larger than normal brains (for 'reptiles'), so they must have been endothermic. Given: Studies indicate that large brain size is correlated with endothermy. Similarly, some modern ectotherms, chameleons for example, have an erect posture. Some endotherms have a more sprawling posture (such as many small mammals) the earliest mammal relatives (the basal synapsids) certainly did not have an erect posture. The two factors seem to be correlated, but cannot be assumed to always occurtogether. Problem: Erect posture has not been shown to be necessary for endothermy, or vice versa. Hypothesis: Dinosaurs must have been endotherms an erect posture must be indicative of endothermy. Given: Dinosaurs and modern endotherms both had/have erect posture (weight-bearing limbs oriented directly below the body rather than sprawling out to the sides).

Also, just because certain ecological patterns are evident today does not mean that they must have always applied. So the 'Given' has not been conclusively established yet. Problem: We don't know that the 'Given' always applies there have been few conclusive studies of endotherm-ectotherm competition. Hypothesis: Dinosaurs evolved alongside mammals, so they must have been endotherms in order to compete with mammals adequately for the 170 million years that they coexisted. Given: Ecological studies suggest that today's endotherms (mammals and birds) generally outcompete ectotherms in their area. Problem: We do not know how fast dinosaurs really moved. Hypothesis: Dinosaurs were built to move fairly quickly, so they must have had high metabolic rates. Given: Studies on modern animals seem to show that metabolic rate is proportional to maximum rate of locomotion.

We shall list some of these and objectively mention some problems with each.

Bakker and others have presented numerous lines of evidence for dinosaurian endothermy some reasonable, some not so reasonable. Evidence for Endothermy? The Evidence forĭr.

Predator vs prey dinosaur exhibit