Excellent interpretation of the common 'impossible triangle'. The fun is that while the inside object is indeed impossible, while the outside, the bones are set in the same pattern (base bone going over leg bone on the left and going under the other leg bone on the right). This might be a coincidence, but I like it. It fits.
omg! this is amazing because this is the only remaining evidence that it ever existed because Escher had to eat his creation to survive shortly after he decide to bathe in the ocean and was eaten by a shark that swam into a forming volcanic island and was trapped deep inside the the molten rock.... dumb shark.