Whiptail Lizards: Teridae

Whiptail lizards populate portions of San Bernardino County’s Mojave Desert. Some, though not all of them, utilize an uncommon form of reproduction among animals, known as parthenogenesis.
Whiptails are of the family Teiidae. Whiptails can be distinguished from other lizards by the large rectangular scales that form distinct transverse rows ventrally and their generally smaller granular dorsal scales, as well as head scales that are separate from their skull bones. Furthermore, teiid teeth are solid at the base and “glued” to the jaw bones. All teiids have a forked, snake-like tongue. They all possess well-developed limbs.
Teiids are universally terrestrial and diurnal, and are primarily carnivorous or insectivorous, although some  include a small amount of plant matter in their diet. They all lay eggs, with some species laying very large clutches.
Certain genera of whiptail lizards have all-female or nearly all-female populations. These lizards reproduce by parthenogenesis.
Parthenogenesis is a form of asexual reproduction in which growth and development of embryos occur without fertilization. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell.
Teiids include the parthenogenic genera Cnemidophorus and Aspidoscelis, which account for about 75% of the species, as well as the  non-parthenogenic Tupinambis
Cnemidophorus and Aspidoscelis are entirely female genera. They simulate the copulation that takes place between the heterosexual Tupinabis. They effectuate this by  one female lying atop  another, engaging in pseudocopulation. There is a disputed theory among scientists that the simulated mating behavior increases fertility. Interestingly, the lizard that was on the bottom has larger eggs, while the one on top has smaller one. The lizards alternate their roles during each mating season. The offspring are genetic clones of their mother

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