Encountered this in the woods last January. The oak was 16" in diameter and the dead loblolly pine stem was 2" in dia. I would say it had been dead for 2-3 yrs. The appendage on the oak is part of the stem, not another stem that fused with the trunk. Took me awhile to visualize the event that caused this. Im guessing the oak is 30-35 yrs old and the pine was 8-10 yrs old.