tpo4

In the reading passage, it indicates that the dinosaurs are endotherms, and it gives three reasons. However, in the lecture, the professor said that many researchers have doubts on these three points, and she explained their arguments specifically.

First, in the reading, the discovery of polar dinosaurs could give evidence to support the theory that dinosaurs are endotherms, because reptiles cannot survive in such low temperature. But the presenter explained that the solar climate back in that time was much warmer than today. Even in the polar season which was the colder than other seasons, dinosaurs could migrate to other warmer areas or hibernate like the reptiles do nowadays.

Second, the leg position under their body could provide convenience for dinosaurs to run, which is a sustained physical activity that could support the hypothesis of endotherms. In the listening passage, the professor suggests that the position of legs might have another explanation that they are used to support more weight of themselves. So, this means dinosaurs may not use their underneath legs for running.

Finally, the third reason of letting some people believe in the topic of dinosaurs are endotherms is the presence of Haversian canals in their fossilized bones, which is a symbolic characteristic of endothermic animals that could allow rapid growth rate. In the presentation, the professor expressed that there also exist growth rings on bones, which could tell the growth rate of the animal in different periods of time. The growth rings on the fossils of dinosaurs show that they endured slower growth rate in cooler periods and higher growth rate in hotter periods. Endotherms could grow in a smoothly rapid speed no matter what the weather would be like. Therefore, the bone structure could not benefit the theorem of endothermic dinosaurs, and they are not so different from the reptiles today.