It is a very healthy root emerging from higher up the trunk than it's lower root buddies. Got one just like it here on a Pak. m/b that rooted through the bottom holes in it's pot. I cut the pot away and the orange root that looks like a tail remains. If that were my tree that split, I would consider to do some Winter pruning on outer branches that might otherwise continue to pull on the trunk to split it farther apart. Decreasing the outer weight of the total branch structure just might stop the threat of additional splitting. Also, try to find out if any neighbors have been studying karate chops on Youtube and ran out of skinny boards to practice on.