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 tw o or three species of morphologically similar, small-bodied lizards distrib uted from southern Peru and Bolivia to northern Argentina and Chile. Recent ly, a few populations of L. alticolor from northwestern Argentina were repo rted to be reproductively bimodal-having both oviparous, and viviparous fem ales at the same locality. We reexamined lizards from these putatively bimo dal populations and found evidence that these populations include two sympa tric yet distinct species-one oviparous, the other viviparous, These specie s can also he distinguished from L. alticolor sensu stricto from the type l ocality (Tiahuanaco, Bolivia). Here we describe the two new species, L. ram irezae and L. pagaburoi, from the province of Tucuman, Argentina. Liolaemus ramirezae differs from L. alticolor in having distinct neck folds, precloa cal pores in females, and an oviparous reproductive mode, and in lacking bo th spots on the throat in males and a vertebral line. Liolaemus pagaburoi d iffers from L. alticolor in having distinct paravertebral marking, slender dorsal stripes, and more rugose head scales, Recognition of these new speci es as distinct resolves the paradox of reproductive bimodality in L. altico lor, Interestingly, both of the new species appear to be microhabitat speci alists that associate with a single species of plant in their respective ha bitats. As predicted by the cold-climate hypothesis, the oviparous species Is distributed in a warmer climate than is the viviparous species.