They shouldn't be. They should be the common ancestor of some critter on down the road.
That brings up a question. Are there any common ancestors that aren't extinct? I mean, sharks have been around for something like 200 million years. Certainly they should be the common ancestor to something.
"Are there any common ancestors that aren't extinct?"
Yeah, there are, for several branches of creatures.
Some goofy-looking proto-horse comes to mind as the common ancestor of donkey, zebras, and horses.
There are also a lot of diverse insects and crabs with living common ancestors.
In the plant family, there's the common ancestor of broccli, asparagus, and caulflower --- but that doesn't really count as those three species are are the result of artifically-induced evolution by man.