TPO 4 Endotherms

Endotherms are animals that keep their body temperature constant. It was long assumed that dinosaurs were not endotherms like other reptiles. However, that was until the appearance of evidence such as the dinosaur fossils discovered in the Polar regions, the position of legs, and the bone structures which suggests that dinosaurs were endotherms. Despite that, the lecture tends to be contrary to the passage.

First of all, several explanations show that discovering dinosaur fossils in the Polar regions doesn’t necessarily mean that dinosaurs are endotherms. Although dinosaurs would have to maintain their internal temperature in order to survive in cold climates like the Polar region, the Polar regions back then were much warmer then nowadays which allows non-endotherms to survive. Moreover, if during cold periods of the year, those dinosaurs could just migrate to warmer places or hibernate like other non-endotherms. Therefore, the presence of the dinosaur fossils in the Polar regions doesn’t prove that dinosaurs are endotherms.

Second, the connection between endothermy and the position of legs has nothing do with the leg position of dinosaurs. Despite the fact that endotherms will have to develop legs under their body for running, a huge aspect of the physiology of endothermy, it doesn’t necessarily mean that dinosaurs would have to be endotherms to have this kind of aspect. Dinosaurs in fact needed this kind of leg position beneath their body in order to support huge weight, making them grow bigger. Thereby, the theory of endothermy will not be considered in discussing the reason why dinosaurs have legs under their bodies.

Finally, the bone structures of dinosaurs don’t mean that they’re endotherms. Although the dinosaurs do have Haversian canals in bone that they have in common with other endotherms, they have a structure in their bones called growth rings which determines that they are non-endotherms. These growth rings have a pattern of rapid growth, following no growth or slow growth during cold periods, then rapid growth again. This indicates that dinosaurs are not endotherms because endotherms would have a rapid growth ring all year long even in cold periods. Therefore, the bone structure of dinosaurs doesn’t mean anything.