Wiktionary
paleomammalian
a. Of or relating to those structures of the brain's limbic system that (according to the triune brain model) arose early in mammalian evolution and were responsible for the motivation and emotion involved in feeding, reproductive behavior, and parental behavior.
Usage examples of "paleomammalian".
Thus, for example, the paleomammalian brain includes and envelops the reptilian brain, but dinosaurs are much bigger than mammals.