因为它们是两足动物，它们的手臂可以自由地进化出拍打的翅膀，这在当时的爬行动物中是不可能的。
Because they were bipedal, their arms were free to evolve flapping flight, which cannot be said for other reptiles of their time.
从那以后，科学家们已对许多深层同源性的案例有了更为详细的认识。 比如卡洛尔博士和他的同事们最近就弄清楚了果蝇翅膀上的斑点是如何通过模块功能置换而进化出来的。
Dr. Carroll and his colleagues, for example, recently figured out how the spots on a fly’s wing evolved through rewiring modules.
现在问题来了，为什么在庞大的恐龙族谱中，有这样一个分支会先进化出如此古怪的外表而不是翅膀呢？
That did raise the question, though, of why one twig of the great dinosaur tree had developed such strange outer vestments, even before it developed wings.
要知道，虽然蝙蝠和鸟类利用翅膀飞行的原理都一样，然而它们的翅膀却是沿着不同道路进化而来的。不同动物的识数能力也可能是在各种不尽相同的情况下分别进化出来的。
Just as bat and bird wings evolved separately yet work using the same fundamental principles, numerical representation may have developed in many separate instances.
最早的鸟类是从树上向地面滑翔的树栖生物，还是因进化出了翅膀而逐渐喜欢长距离跳跃的两足陆生动物？
Were the first flyers arboreal creatures that initially glided from tree tops to the ground? Or were they bipedal ground runners whose evolving wings allowed them to take progressively longer jumps?
最早的鸟类是从树上向地面滑翔的树栖生物，还是因进化出了翅膀而逐渐喜欢长距离跳跃的两足陆生动物？
Were the first flyers arboreal creatures that initially glided from tree tops to the ground? Or were they bipedal ground runners whose evolving wings allowed them to take progressively longer jumps?
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