Basal vs Derived

The terms "basal" and "derived" are relative. They only make sense if you provide the context - what clade are you talking about?


 * Basal animals have the traits required to belong in their clade, but otherwise have a lot in common, still, with that last common ancestor that unites the clade.


 * Derived animals have features really different from the last common ancestor at the base of their clade.

Examples:


 * Coelophysis is a derived tetrapod, but it's a basal dinosaur.
 * Archeopteryx is a derived dinosaur, but it's a basal bird.

Come up with your own examples. Within any clade of animals, what is a good example of a basal animal? What is a good example of a derived animal?