The aggressive carnivorous reptiles in this tessellation are based on Roger Penrose’s “Jigsaw Puzzle” tiles. The reptiles form closed circles, facing alternately inwards and outwards.. It seems impossible to hold all the circles in view at once, instead by shifting attention, one can see clearly only the blue, ochre or green circles at any one time.

Doris Schattschneider, in her book Visions of Symmetry, describes Penrose sending his Jigsaw Puzzle tiles to Escher as a wooden puzzle as a challenge for him to solve. Escher was successful, and eventually produced “Ghosts” his last symmetry drawing in 1971 based on the tiles. It is probably one of Escher’s least exciting tessellations and shows the challenge in the restrictive edge matching rules inherent in complex tilings. The tiling is anisohedral, with only a single edge profile used, although in mirrored form.