As if being able to re-grow a tail isn't cool enough, some species of whiptail lizards (genus Cnemidophorus) have another trick: They can clone themselves. These species actually consist completely of females able to reproduce by parthenogenesis.

The original sexless females, known as parthenogens, come from the hybridization of two separate lizard lines. The parthenogen has one copy of chromosomes from its mother, and one analogous but slightly different copy from its father. It can give rise to offspring that are their exact clones, without their two genetic copies recombining.

Asexual whiptails have a special trick for making spermless reproduction work: The egg cells in other animals first double their choromosomes once and then divide twice, leaving them as haploid cells, with half the normal number of genetic material. But the whiptails' egg cells first double their chromosomes twice and then divide twice, leaving them with the normal number of chromosomes and rendering a sperm cell unnecessary.

Pairs of female whiptails sometimes engage in mock sex, which led to the nickname "lesbian lizards" and seems to encourage the production of egg cells. But they do seem to have some interest in the opposite gender: Sometimes these parthenogens are mate with males of different species, creating a species with 50 percent more genes than normal.