But now we know that some toothed birds were able to fly, so it wasn't like having teeth was keeping them on the ground.

但现在我们知道有些有齿的鸟能够飞翔，所以牙齿并不是让它们留在地上。

So today, we finally have enough fossils of different kinds of birds to know that, about 66 million years ago, there were both toothed birds and toothless birds from many different groups.

所以今天，我们终于有了足够多的不同种类鸟类的化石，可以知道，大约在 6600 万年前， 有许多不同种群的有齿鸟类和无齿鸟类。