SOME DINOSAURS WERE LIKELY TO BE WARM BLOODED
Dinosaurs belong to class Reptilia and so for many years scientists thought that they were cold blooded, with slow metabolisms and dominated the planet for about 135 million years. However, birds evolved from small carnivorous dinosaurs of the Late Jurassic, with fast metabolic rates, raising the question of whether or not their extinct dinosaur relatives were also warm-blooded.
Whether the extinct dinosaurs were ectothermic or endothermic or combination of both to some extent is one of the greatest controversies in paleontology. Every possibility is supported by groups of scientists with reasonable evidences. Ectothermy in dinosaurs is assumed to be ectothermic by default condition as the ancestors …show more content…
Dinosaurs were quite large but they did not need to be endotherms; they could be homeotherms; they would warm up slowly and cool very slowly, so they could maintain a near-constant body temperature.
3. The bone structure of some dinosaurs exhibit lines of arrested growth, showing that growth was seasonal. Modern endotherms do not have of arrested growth, and modern ectotherms have.
4. Ectotherms are generally scaly. Dinosaur fossilized skin impressions show somewhat scaly hides.
5. The absence of nasal respiratory turbinates in dinosaurs indicates that they were likely to have maintained reptile-like metabolic rates during periods of rest or routine activity.
But there are also several logics which indicate these hypotheses may be false.
• The climate in the Mesozoic era was varied, and dinosaur fossils are found in some areas that were cooler and less mild then, including high altitude and polar regions.
• Not all adult dinosaurs were large. The weight range was from about 5 kg to 80 or so tons. Even the largest dinosaurs would have had small babies. Animals can have ways of regulating heat that the fossil record does not preserve such as behavioral (stay out of the sun), physiological (special enzymes), anatomical (big ears to radiate
Dinosaurs belong to class Reptilia and so for many years scientists thought that they were cold blooded, with slow metabolisms and dominated the planet for about 135 million years. However, birds evolved from small carnivorous dinosaurs of the Late Jurassic, with fast metabolic rates, raising the question of whether or not their extinct dinosaur relatives were also warm-blooded.
Whether the extinct dinosaurs were ectothermic or endothermic or combination of both to some extent is one of the greatest controversies in paleontology. Every possibility is supported by groups of scientists with reasonable evidences. Ectothermy in dinosaurs is assumed to be ectothermic by default condition as the ancestors …show more content…
Dinosaurs were quite large but they did not need to be endotherms; they could be homeotherms; they would warm up slowly and cool very slowly, so they could maintain a near-constant body temperature.
3. The bone structure of some dinosaurs exhibit lines of arrested growth, showing that growth was seasonal. Modern endotherms do not have of arrested growth, and modern ectotherms have.
4. Ectotherms are generally scaly. Dinosaur fossilized skin impressions show somewhat scaly hides.
5. The absence of nasal respiratory turbinates in dinosaurs indicates that they were likely to have maintained reptile-like metabolic rates during periods of rest or routine activity.
But there are also several logics which indicate these hypotheses may be false.
• The climate in the Mesozoic era was varied, and dinosaur fossils are found in some areas that were cooler and less mild then, including high altitude and polar regions.
• Not all adult dinosaurs were large. The weight range was from about 5 kg to 80 or so tons. Even the largest dinosaurs would have had small babies. Animals can have ways of regulating heat that the fossil record does not preserve such as behavioral (stay out of the sun), physiological (special enzymes), anatomical (big ears to radiate