Two new cryptic species of Liolaemus (Iguania: Tropiduridae) from northwestern Argentina:: Resolution of the purported reproductive bimodality of Liolaemus alticolor

The Liolaemus alticolor group (Iguania: Tropiduridae) currently includes two or three species of morphologically similar, small-bodied lizards distributed from southern Peru and Bolivia to northern Argentina and Chile. Recently, a few populations of L. alticolor from northwestern Argentina were reported to be reproductively bimodal-having both oviparous, and viviparous females at the same locality. We reexamined lizards from these putatively bimodal populations and found evidence that these populations include two sympatric yet distinct species-one oviparous, the other viviparous, These species can also he distinguished from L. alticolor sensu stricto from the type locality (Tiahuanaco, Bolivia). Here we describe the two new species, L. ramirezae and L. pagaburoi, from the province of Tucuman, Argentina. Liolaemus ramirezae differs from L. alticolor in having distinct neck folds, precloacal pores in females, and an oviparous reproductive mode, and in lacking both spots on the throat in males and a vertebral line. Liolaemus pagaburoi differs from L. alticolor in having distinct paravertebral marking, slender dorsal stripes, and more rugose head scales, Recognition of these new species as distinct resolves the paradox of reproductive bimodality in L. alticolor, Interestingly, both of the new species appear to be microhabitat specialists that associate with a single species of plant in their respective habitats. As predicted by the cold-climate hypothesis, the oviparous species Is distributed in a warmer climate than is the viviparous species.