Here are other later groups of the avians. Note that not all of the groups fly, but more importantly how they look in relation to modern birds and ancient birds. Also have a look at the time scale relationships on the next page.

NAME: Hesperornithiforms (wingless swimming birds), Are Marsh's birds of the Cretaceous found in Kansas. They are structurally almost identical to ducks, but with teeth. They are younger than the Archaeopteryx. Wether they are branching from the ancient bird or are a side evolution path, it is still uncertain. The one important thing is that it is more developed in structure than the earlier birds (ie Archaeopteryx).

NAME: Ichthyornithiform Is another group that does not fly. Again more structurly similar to modern birds than the Archaeopteryx.