Time for thoughts, guesses, and just opinions?
Really after leaves and bark are gone and not seeing it under some particular tree, it can be nearly impossible to tell the species. But on the other hand, that may not matter at all. We CAN be sure of a couple things. They are not new Cedar, pine or one of the trees which are famous for holding sap so we can move on as very few types are dangerous when fully dry. They could be oak on the left two in the first pic. Maybe not on the right two?? It looks from here, that you have chosen very well.
They are not large thick pieces so the drying is much faster than a four inch thick might be. The cracks are a good sign as they form when the wood dries and shrinks. That one crack looks like it might extend all the way to the middle. That one is almost certain to be good!
If you cut an end off or shorten them, check for pretty uniform color outside to inner. The more uniform the more likely to be totally dry.
In the fourth pic of the broken end, I see what looks like a borer of some type. I don't like to put unknowns into the tank, whether they would do any harm or not. I like to KNOW it is clean and dead. That means I do an overnight soak in water with a 1/2 cup or so of bleach. Then I pull it out, rinse it and let it dry. Then I can use it without worry about what unknown might be in there hiding. Like my dinner plate, I feel better knowing it is safe rather than kind of/sort of hoping it is.
I would give you an "A" in wood hunting class!!