Three living species X, Y, and Z share a common ancestor T, as do extinct species U and V. A grouping that consists of species T, X, Y, and Z (but not U or V) makes up
When referring to phylogeny a group can be considered paraphyletic when it includes the common ancestor, but it does not include all the descendants from this common ancestor.
The group is (T, X, Y, and Z), the other group is (U and V) and they both share a common ancestor (T).
The use of paraphyletic group is still controversial. Some accepted and other don't.
