Gigantothermy (sometimes called ectothermic homeothermy or inertial homeothermy) is a phenomenon with significance in biology and paleontology, whereby large, bulky ectothermic animals are more easily able to maintain a constant, relatively high body temperature than smaller animals by virtue of their smaller surface-area-to-volume ratio.
[2] The phenomenon is important in the biology of ectothermic megafauna, such as large turtles, and aquatic reptiles like ichthyosaurs and mosasaurs.
[3] Gigantothermy allows animals to maintain body temperature, but is most likely detrimental to endurance and muscle power as compared with endotherms due to decreased anaerobic efficiency.
[4] Mammals' bodies have roughly four times as much surface area occupied by mitochondria as reptiles,[clarification needed] necessitating larger energy demands, and consequently producing more heat to use in thermoregulation.
Consequently gigantothermic ectotherms would not have to eat as often as large endotherms that need to maintain a constant influx of food to meet energy demands.