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2024-10-29 02:29 本頁面
【正文】 s mammals and birds. First, as demonstrated by a stony heart recently found in South Dakota in 1993 by a private fossil collector, dinosaurs could have evolved a heart adapted to warmblood circulation. Although the fact that soft tissues usually deposed before they could fossilize had left scientists searching in darkness for centuries, fossil ans could still be preserved under extreme circumstances such as rapid sediment on the seabed. Because today fourchambered heart is only found in warmblooded animals, this fossil heart indicates the close relationship between dinosaurs and mammals. Second, because coldblooded animals such as reptiles couldn39。t maintain their body temperature constantly, they have to rely on the surrounding environment to adjust the body heat. Thus, if dinosaurs are coldblooded, their huge body size would make it impossible to shift between basking and burrowing as often as today39。2020年 10月 8日 Although dinosaurs are traditionally believed to be coldblooded reptiles, such as crocodiles, lizards and sea turtles, evidences recently discovered have implied a picture on quite the opposite side. Scientists today are more readily to believe that there is a good chance for dinosaurs to be warmblooded animals, like today39。s lizards. Third, for huge body animals to maximize their energy usage, they must maintain a constant body temperature. This is because metabolism is in fact a chemical process occurring in the body, which burns food intake and releases energy supporting growth. For this chemical reaction to function optimally, keeping ans working at certain temperature is a necessity. Male Professor You all heard about that….warm blooded dinosaurs theory. It sounds like a science fiction, doesn’t it? I must be honest to admit that I am not going to accept this warmblooded theory, although quite some of my colleagues do. To me and many other researchers, dinosaurs are doubtlessly close relatives of coldblooded reptiles, only much bigger. First, it is said that a fourchambered stony dinosaur heart had been discovered, but how could we identify that the heart belongs to an extinct dinosaur, rather than from an ancient mammal? We all know that more than often, different animal skeletons are discovered blended together at one single fossil site. Second, I don’t think dinosaurs had to rely on the environment to adjust their body temperature as much as lizards and snakes do today. Don’t fet, when dinosaurs dominated this pla, the climate was much milder than it is today. Air temperatures shifting between high and low extremes were rarely recorded. Third, yes, it is true that large animals must keep a constant body temperature to maximize the energy released from food intake. But a stable body temperature isn’t necessarily proof of warmbloodedness, since even some coldblooded animals like giant sea turtles could keep body temperature constantly. This is because their ratio of surface area to volume is relatively low, minimizing heat excha
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