Tropidosaura essexi Hewitt, 1927 (Reptilia: Lacertidae) is live bearing: the only viviparous African lacertid

Abstract

Viviparity has evolved independently multiple times within squamate reptiles. In the Lacertidae, two genera and several species from the Northern Hemisphere are known to be viviparous. However, although viviparity is present in many African reptiles, all African lacertids were considered exclusively oviparous. The lacertid genus Tropidosaura is restricted to mountainous grassland habitats across central and southern South Africa. Prompted by the dissection of a gravid T. essexi specimen containing well-developed embryos, we dissected additional gravid females from two museum collections to assess parity mode in the four Tropidosaura species. Gravid females of three species contained developing eggs, but all gravid Tropidosaura essexi specimens examined exhibited simple placental development or contained well-developed embryos with the presence of a simple placenta and an absence of any eggshell. The large yolks and simple placentae suggest that viviparity in T. essexi is lecithotrophic. T. essexi thus represents the only known viviparous species of lacertid in Africa and therefore, the first known viviparous lacertid in the Southern Hemisphere, revealing yet another independent case of the evolution of viviparity within the squamates. T. essexi occurs at higher maximum elevations than any of its oviparous congeners, and the recorded litter size in T. essexi was slightly higher than the clutch sizes of other members of the genus. Previously reported oviparity in T. essexi may either be the result of specimen misidentification or potential bimodal reproductive in this species, but this latter explanation is unlikely, given that none of the T. essexi examined in this study showed evidence of oviparity.