
A nurse log... It is common to see trees where the nurse log has entirely rotted away, living the roots supporting the tree in thin air....
There's one near us, on the McLane Park Nature Trail, where you actually walk on the trail underneath the roots, where a very large nurse log has completely rotted away. The space beneath the beginning of the trunk is over 6 feet tall. And the roots on either side look like large legs (after enough beer, that is).