The genus Xenopus is an exception in the animal world. While it is true that most animals are diploid (having two sets of chromosomes), there are no extant (living) species within the Xenopus taxon that are diploid (unless you consider Silurana tropicalis to be a part of Xenopus). Xenopus laevis, which is the most common species in the pet trade is actually tetraploid (having 4 sets of chromosomes). The strangest species of all are Xenopus ruwenzoriensis and X. longipes, both are dodecaploid (having 12 sets of chromosomes). Really weird, you would expect to see these numbers in the plant kingdom.