So we were filling in lots of gaps.

所以我们填补了很多空白。

Because, they used to face some pretty stiff competition from a group of lizard look-alikes -- basically, lizard impostors that went around filling a lot of niches that modern lizards occupy today.

因为，他们曾经面临来自一群蜥蜴相似者的激烈竞争——基本上，蜥蜴冒名顶替者四处走动， 填补了现代蜥蜴今天占据的许多壁龛。