Metabolism of Dinosaurs

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In essence, Dinosaurs were initially understood to be cold-blooded animals. However, new research on their development proposes that the beasts grew similarly as fast as mammals, showing that they were warm-blooded animals. But, not everybody concurs with the conclusion, citing that since Dinosaurs were not lethargic like lizards or high-energy like the mammals; they were somewhere in the middle (Brett-Surman, Holtz, & Farlow, 2012). This implies that there is an intermittent middle ground in the debated about whether dinosaurs were ectoderms, using their environment in regulating their temperature internally or endotherms, regulating their body temperature internally.

                                    So were dinosaurs endotherms?

Dinosaurs were not by any chance exclusively endotherms. Many paleontologists argue that dinosaurs fell between endotherm and ectotherms range, making them be mesotherms or rather, the intermediate-blooded. Today, a similar middle ground can be exhibited by animals such as lamnid sharks, the leatherback sea turtles and tuna (Erickson, Rogers, & Yerby, 2001).

Dinosaurs are classified as reptiles, so we assume they were cold-blooded like their relatives, which means they relied upon their surroundings to regulate their body temperature. Consequently, the slow metabolism of such cold-blooded dinosaur would have constrained it to move sluggishly across its vast environment (Grady, Enquist, Dettweiler-Robinson, Wright, & Smith, 2014). A warm-blooded dinosaur, notwithstanding, would have controlled its own body temperature and been armed with a speedier metabolism. Such an animal could have easily moved around its habitat.


                                                   The debate

Scientists have long debated thermoregulation in dinosaurs, yet the new debate started with a 2014 report in the journal Science suggesting that dinosaurs were most likely mesotherms. Actually, past investigations on dinosaurs' energy rates, consumption and teeth likewise have discovered suggesting evidence they were mesotherms (Hillenius, 2006). The response to this question isn't only for scientific journals; fairly, it would paint an entire picture of how dinosaurs lived and died.

While trying to settle the debate, scientists examined fossilized dinosaur bones. These bones have growth rings which are similar to the rings of a tree and are believed to show how slowly or quickly the creatures grew (Pontzer, Allen, & Hutchinson, 2009). The scientists compared the growth rate of dinosaurs and those of both the living and extinct animals and found that the dinosaurs fell in the middle of the growth range between ectotherms and endotherms. This led us to mesotherms.

As indicated by many researchers, some dinosaurs were mesothermic and endothermic, however, investigations of particular clades (species that share a similar ancestor), time periods and environments showed separate growth and metabolism rates. There are a variety of hints that nonavian dinosaurs lived very vigorous, active lives that are analogous to mammals and birds. For example, some had anatomy signifying that they ran quickly, and others abandoned trackways indication that they migrated just like mammals.

                                          Dinosaur’s metabolism

To help settle this decades-old puzzle, specialists developed another strategy for further breaking down the metabolism of extinct animals (Brett-Surman, Holtz, & Farlow, 2012). They discovered that dinosaurs don't fit serenely into either the ectotherm or endotherm camp. Essentially, Scientists regularly try to derive the metabolic systems of extinct creatures by examining the rates of body growth which bear a resemblance to cutting into a tree and then examining the ring thickness, which definitely uncovers how well or ineffectively a tree developed at a particular period.

Research has looked at growth rings in fossils, as well as tried to evaluate the rates of metabolism by examining the changes in the size of the body as they grow into maturity. They have examined a wide range of animals, both living and extinct species, both warm-blooded and cold-blooded animals, and dinosaurs (Erickson, Rogers, & Yerby, 2001). The researchers found the rate of growth to be an indication of the rate of metabolism in living creatures, from birds to sharks.

Consequently, as the researchers studied how quick dinosaur’s growth was, they found that the creatures didn't look like vertebrates or the modern reptiles, as such were neither endotherms nor ectotherms. Rather, dinosaurs fall in the middle, making them the "mesotherms." There has been an exceptional range of skeletons for some of the species, indicating the development of mammals, and the rates give a phenomenal impression; from hatchling to mature Hadrosaurus in just 5 years. This rate is affirmed by the study of growth rings in bone. Such speed is feasible for both cold-blooded and warm-blooded animals.

                                  Evidence from modern mesotherms

Similar to the dinosaur, that kind of energetically intermediate animals are not very common, yet they exist. For example, white shark, leatherback turtle, and tuna are basically mesotherms, similar to echidna (Grady, Enquist, Dettweiler-Robinson, Wright, & Smith, 2014). Like vertebrates, mesotherms produce adequate heat to keep their blood warmer than their condition, however, similar reptiles today; they don't sustain a constant temperature.

Body size can play a critical role in mesothermy since larger creatures can preserve heat much effectively. For example, leatherback turtles are mostly mesotherms, while green sea turtles are smaller and definitely not mesotherms. In any case, mesothermy is not dependent on size only. For instance, while Mako sharks are mesotherm, whale sharks are ectotherms (Hillenius, 2006). Also, the body temperature of Tuna decreases while jumping into deep, colder waters, but remains higher than the surrounding water.

Endotherms are able to enhance their metabolisms to heat up for example; we shake when freezing, which produces heat. On the other hand, Mesotherms has modifications to preserve heat; however, they don't shiver or burn fat to warm up. They do not increase metabolism to remain warm (Pontzer, Allen, & Hutchinson, 2009). Some of the animals are called gigantotherms, which means they are simply so big that they preserve heat despite the fact that they don't effectively regulate their body temperature.

                                Advantages of mesothermy to the dinosaur

Mesothermy might have allowed dinosaurs to be able to grow, reproduce and move faster as compared to their ectothermic kin, making them more precarious predators and slippery prey. This explains why dinosaurs ruled the world up until their eventual extermination around 65 million years to this day (Erickson, Rogers, & Yerby, 2001). Similarly, dinosaurs' lower metabolism compared with mammals enabled them to live on a lesser amount of food.

Therefore, this might at that time allowed the tremendous mass majority of dinosaur species achieved. For example, it’s uncertain that a lion of Tyrannosaurus’ size would have had the capacity to eat elephants or wildebeests enough to sustain it without starving to death (Grady, Enquist, Dettweiler-Robinson, Wright, & Smith, 2014). With their lower food consumption, be that as it may, a Tyrannosaurus could get by fine and dandy.


From the characteristics above, it is evident that dinosaur is mesotherms since they fall in the balance between endotherms and ectotherms. However, it is worth noting that although mesothermy seems prevalent among dinosaurs, not all dinosaurs were fundamentally mesotherms.




Brett-Surman, M. K., Holtz, T. R., & Farlow, J. O. (2012). The complete dinosaur. Bloomington, IN: Indiana University Press.

Erickson, G. M., Rogers, K. C., & Yerby, S. A. (2001). Dinosaurian growth patterns and rapid avian growth rates. Nature, 412(6845), 429-433. doi:10.1038/35086558

Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2014). Evidence for mesothermy in dinosaurs. Science, 344(6189), 1268-1272. doi:10.1126/science.1253143

Hillenius, W. J. (2006). Dinosaur Physiology: Were Dinosaurs Warm-blooded? Encyclopedia of Life Sciences. doi:10.1038/npg.els.0003323

Pontzer, H., Allen, V., & Hutchinson, J. R. (2009). Biomechanics of Running Indicates Endothermy in Bipedal Dinosaurs. PLoS ONE, 4(11), e7783. doi:10.1371/journal.pone.0007783

October 05, 2023

Life Science



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