How big is the leaf? If they're as big as they look in the pic, and the "mitten" isn't just a fluke, definitely sass. The leaf arrangement in the pic almost suggests ash, and the bark looks similar to the massive green ash I hauled from my neighbors house. But the veins in the leaf give it away for me, as sass. The extra "mid-veins" often end up forming the "thumb" of the mitten.
Thx guys! I ended up moving to the oaks I posted about on Sunday. Come the first heavy frost, the cover on the floor of the forest will be reduced revealing much more downed stuff. Don't know if I should be happy or sad.