Question: What is the common ancestor of mammals and birds name?

Anthony Redmond answered on 14 Jan 2019:

Birds and mammals both belong to a group of vertebrates called amniotes, named after a special membrane that allows offspring to be brought to term outside of water (useful if you live on land!). If you have heard of ‘waters breaking’ at the end of human pregnancy, this fluid, which is actually amniotic fluid (and helps with exchange of important things like water and nutrients between mother and fetus), is what is released when this membrane breaks.

Anyway, this term (amniote), is used to describe all vertebrates that have evolved from within this group, including all reptiles, birds, mammals, and some of their extinct relatives. So, we would call the most recent common ancestor of birds and mammals is the most recent common ancestor of amniotes. We could probably get away with just ‘amniote ancestor’ most of the time, but we would need to remember that this could be taken to include extinct relatives, that might be little more distantly related!

Another thing to remember is that mammals and birds do not share a most recent common ancestor excluding other animals. You might have heard before that birds actually evolved from reptilian ancestors, are are closely related to dinosaurs. Of those living groups however, crocodiles are most closely related to birds, followed by turtles, then lizards and snakes, and then mammals! But, mammals (including ourselves), are equally closely related to all of those other groups! So our common ancestor with birds (the most recent amniote common ancestor) is also shared with all of those species!