TPO4

The reading claims that dinosaurs differ in many ways from modern reptiles, and there is now considerable evidence that dinosaurs were endotherms and it provides three reasons of support. However, the professor states that many scientists have problems with the arguments in the passage and she refutes each of the author's reasons.

First, the article avers that dinosaur fossils have been discovered in polar regions so dinosaurs could maintain their body temperature. In contrast, the speaker opposes this point by saying that it is true that dinosaurs lived in polar regions, but the climate was much warmer that before. In addition, she mentions that during cold weather, dinosaurs could migrate to a warmer region, or habrinated, so this approves that dinosaurs are not endotherms.

Second, the passage posits that the legs of all modern endotherms are underneath the body, and so were the legs of dinosaurs. This strongly suggests that dinosaurs were endotherms. On the other hand, the lecturer counters this point by stating that the position of legs doesn't necessary to be a proof of that. In fact, she mentions there is another explanation for this point. She argues that the legs support the body wieght so dinosaurs can grow in a large size. This appears that dinsaurs were not endotherem.

Third, the article asserts that the presence of Haversian canals in bones of dinosaurs is a strong indicator that the dinosaurs were endotherm. Conversely, the professor casts doubt on this point by explaining that it is true that dinosaurs have Haversian bones, but dinosaurs also have growth rings and this indicates that they were not rapidly grow. Actually, they stopped growing or they grew slowly and this pattern of rapid grew, slow grew, then rapid grew is a characteristic of none endotherm animals.