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2006年10月8日Although dinosaurs are traditionally believed to be cold-blooded 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

warm-blooded animals, like today'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 warm-blood circulation. Although the fact that soft tissues usually decomposed before they could fossilize

had left scientists searching in darkness for centuries, fossil organs could still be preserved under extreme circumstances such as rapid sediment on the seabed. Because today four-chambered heart is only found in

warm-blooded animals, this fossil heart indicates the close relationship between dinosaurs and

mammals.

Second, because

cold-blooded animals such as reptiles couldn't maintain their body temperature constantly, they have to rely on the surrounding environment to adjust the body heat. Thus, if dinosaurs are cold-blooded, their huge body size would make it impossible to shift between basking and

burrowing as often as today'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 in-take and releases energy supporting growth. For this chemical reaction to

function optimally, keeping organs 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 warm-blooded theory, although quite some of my colleagues do. To me and many other researchers, dinosaurs are doubtlessly close relatives of cold-blooded reptiles, only much bigger. First, it is said that a four-chambered 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

forget, when dinosaurs dominated this planet, 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 in-take. But a stable