 For a long time, the sphinx was widely believed to be the only example known, but the German/New-Zealand mathematician Karl Scherer and the American mathematician George Sicherman have found more examples, including a double-pyramid and an elongated version of the sphinx.These pentagonal rep-tiles are illustrated on the Math Magic pages overseen by the American mathematician Erich Friedman.However, the sphinx and its extended versions are the only known pentagons that can be rep-tiled with equal copies.