So why the change in theory? One idea just actually comes from looking at those teeth. They're actually designed for crunching through bone, but if we compare that with another meat-eating dinosaur tooth, a dinosaur called Megalosaurus. And this is much more like an actual steak knife, whereas these things are like railroad spikes. This suggests that the T Rex was actually a specialist bone crushing dinosaur, so maybe it was bone crushing because it was hunting. They might have just been bone crushing because it was eating carcasses. What about the arms that those pathetic little front arms? Are they giving any clues? They're obviously not there for feeding, 'cause they couldn't even reach the mouth of the animal. The best idea we have for these to the arms is either there's something called a vestigial structure. That is a structure that's been is kind of disappearing through evolution. So they're on their way out? Exactly. Or maybe they're something to do with mating, and actually they're used for holding on.


那么为什么理论会变化？ 是因为对这些牙齿的观察，它们本该用来嚼碎骨头。但如果我们把这些牙齿。斑龙，又名巨龙。巨齿龙生于侏罗纪晚期，和另一种食肉龙，斑龙的牙齿比较，斑龙齿更像是牛排刀。而这些则像是铁路道钉，这说明霸王龙大概只擅长咬碎骨头。这有可能是为了捕食活物，但也可能是为咬碎尸体。 它短得可怜的前肢呢？ 能说明什么吗？ 霸王龙前肢不是用来捕食的，它们够不到霸王龙自己的嘴巴。最有可能的两种解释是，要么它是某种残余结构，正在进化过程中逐渐消失， 就是说前肢在退化吗？ 是的，要么就是用来帮助霸王龙交配，用来抓住交配对象。