Anybody know about eyes?

Like garters, nonven-o-mous (that's hard to say!), have round pupils. Many venomous snakes have vertical pupils.

While looking at the Nature Photography thread I saw RepitleParadise's croc picture. They have vertical pupils and are nonvenomous.

Why is there a difference, besides "just because that's the way it its"? Does it have to do, maybe, with further evolving - though I'd be hard pressed to guess which was more evolved - venomous or non.

Are crocs more closely related to rattlers than rattlers are to garters? That can't be as a snake is closer to another snake than a crocodile.

So. Anybody know anything about the difference in pupils?