What's the most recent common ancestor of reptiles and humans?

Question

In the Phylogeny of humans and reptiles, what is/are some of the most recent common ancestors?

Answer 1

I think that you are looking for the amniote common ancestor.

Amniotes are the group of organisms that have an amnion, a specific membrane around the egg, among other features. This includes reptiles, mammals, etc. but excludes amphibians and fish as indicated in your tree.

Wikipedia says:

The first amniotes, referred to as "basal amniotes", resembled small lizards and evolved from the amphibian reptiliomorphs about 312 million years ago,[7] in the Carboniferous geologic period. Amniotes spread around Earth's land and became the dominant land vertebrates.[7] They soon diverged into synapsids and sauropsids, which persist today. The oldest known fossil synapsid is Protoclepsydrops from about 312 million years ago,[7] while the oldest known sauropsid is probably Paleothyris, in the order Captorhinida, from the Middle Pennsylvanian epoch (c. 306–312 million years ago).

That citation 7 points to this paper, which used paleontological data to assign time estimates to various diversification events inferred from molecular phylogenies; this allowed them to approximately estimate the time of emergence of amniotes from the amphibian clade.