Yeah, when I started trying to figure it out by myself via pictures, I realized I need pictures of twigs. Unfortunately (for this purpose anyway) these are all clear up to 20' or higher, so I'm pretty much stuck looking at fallen stuff and it's really hard to be sure what it fell from. I'll have to go back out this weekend and see if there are any similar looking trees with bark that have branches close enough to cut one off for examination.
Last summer I wasn't really considering turning any of them into lumber. My only consideration was their suitability for holding up a couple thousand pounds of treehouse, or a zip line or I'd have attempted to figure this out while they had leaves.