In this, Erythrosuchids constitute an Archosauriformes clade that is an outgroup to the Archosauria proper.

依照这个方法，引鳄科构成一个龙形动物，龙的外群体。

What does group membership mean? How should we measure it? Ingroup vs. outgroup.

群体会员的意思什麽？我们应如何衡量？圈内与圈外。