Portal talk:Tsuinaron/@comment-5362365-20130104015125/@comment-4730598-20130104030947

Quite true, the term I think is needed is Monotreme. These are the only known Gaean mammals that lay eggs.

Another option would be to just call them repto-mammals, which are creatures that have attributes of both reptiles and mammals, i.e. laying eggs and feeding their young with milk.