You have trouble staying in evo mode for long, but I think you're there. The new features can only inherit up the tree. There's no jumping branches or going down.
The ancestors of mammals, Synapsida, branch off that Amniote tree I linked earliest of all. The lineage they left behind does a bunch of branchings thereafter, giving rise eventually to the diapsids, which include dinos and their bird descendants.
T. rex having mammaries would be a case of inheriting from a fifteenth cousin, or more like the future descendants of a fifteenth cousin. Unless T. rexes invented their own which were lost when T. rex died out. An unlikely happening with no evidence.
". . . branch earliest of all off of that tree . . ." Tired.
Forgot to mention that we could move the invention of mammaries back to some common ancestor of T. rex and the synapsids, then figure out some loopy reason no other descendants have the milk glands. (Nah!)
This is not a terribly complicated point. If I didn't address it directly the first time you hinted at it, I guess it's because I was looking for greater subtleties. I'm well aware, as are most creationists, that our ancestors don't inherit from us. (I find it incredible that you think it necessary to expound upon that point.) Indeed, as I think I've demonstrated, I have a fair understanding of evolution, at least in its broad outlines. And although a creationist, I'm not insane or incapable of reason. I do not consider evolutionists to be a gang of fraudulent con artists, and I'm very distressed at the tactics of many other creationists in these threads. I regard evolution as a provisional hypothesis. I don't even get upset when it's taught exclusively in the schools. I think you've taken an unnnecessarily hostile approach in my case, but that's okay. You don't know me.