Colosteids were unique compared to most stegocephalians in the fact that a pair of palatal fangs were present on the premaxillary bones at the tip of the snout.

In conjunction with the forward position of these fangs, the dentary bones of the lower jaw developed a notch on either side near the symphysis (chin).

The mandibles were also unique in the fact that they possessed a single elongated hole along their inner surface, known as an exomeckelian foramen (or a meckelian fenestra).

Earlier stegocephalians like Ichthyostega possessed a subtle slit in the mandible, while most later groups had a series of smaller, well-defined holes.

[3] Panderichthys Elpistostege Tiktaalik Elginerpeton Ventastega Acanthostega Ichthyostega Whatcheeriidae Colosteidae Crassigyrinus Baphetidae Crown group Tetrapoda