Did the common ancestor of birds and mammals have warm blood?

Probably not, but the matter is still being debated. The nearest common ancestor of birds mammals was probably an eight - inch long reptile that lived anywhere between 320 and 340 million years ago. Its an sector 360 million years ago was still a fish, four - footed, with lungs, but relying mainly on gill - breathing, and just occasionally dragging itself on to land for brief periods.