Latitudinal Zonation In Dinosaurs

A controversy always surrounds dinosaur regarding it being ectothermic or endothermic. Mammals and birds use their metabolic heat, muscular shivering mechanism, insulating coat in the form of fat deposits, hair or feathers to maintain fairly constant body temperature within a range of ± 2ºC and are endothermic. On the other hand, reptiles, fishes and amphibians exhibit variation in body temperature depending on the ambient temperature and are ectothermic.
Dinosaurs have been placed in the subclass Archosauria of the class Reptilia and it has been etched in people’s mind that dinosaurs are ectotherms. However, various fossil records and paleontological evidence provide valuable information about the metabolic rates and thermoregulation of dinosaurs.

Paleomagnetic data help to reconstruct the ancient position of continents to within about five degrees of latitude whereas glacial and salt deposits indicate the global latitudinal temperature gradient from poles to the equator. These latitudes and temperature gradient create zones that separate endotherms from ectotherms. Large reptiles cannot survive cold winter conditions existing in the poles because they cannot warm up their body temperature during the short winter day and they are too large to find safe hiding places to hibernate. Small reptiles like small lizards are found as far north as Alberta where they hibernate underground in winter but large reptiles like crocodiles or big lizards do not go beyond northern coast of Gulf of

The ratio is a constant that is characteristic of the metabolism of the predator irrespective of the size of the animals involved in predator-prey system. The energy requirement of endothermic animals are many times greater than that of ectothermic animals but the prey tissue yield available to the predator is same for both an ectothermic or an endothermic population. Therefore, a given prey population either ectotherms or endotherms can support a greater biomass of ectothermic predators compared to endothermic predators as the energy requirement of endotherms are many times higher than that of ectotherms. In both ectotherms and endotherms, the energy value of carcasses produced per unit of energy content in the biomass of a population decreases with increasing weight of adult prey. The energy requirement per unit of predator biomass also decreases with increase in weight. Therefore, if the adult size of the prey is roughly equal to its predator, the maximum ratio of predator biomass to prey biomass in a steady-state community is a constant independent of the body size of predator-prey system. Spiders are ectotherms and ratio of spider population’s biomass to its prey biomass reaches a maximum of 40%. Mountain boomer lizard feeding on lizards would exhibit a similar ratio. On the other hand endothermic animals reach a maximum predator-prey biomass ratio of only 1-3%. Thus predator-prey