With the recent designation of the holotype of Centrura flagellifer Bell as theneotype of Phymaturus palluma Molina by the International Commission on Zoological Nomenclature, the type locality of P. palluma became problematic. It is likely that Charles Darwin collected the holotype of C. flagellifer during his round trip journey between Santiago, Chile and Mendoza, Argentina. A detailed account of his journey is presented, as well as the conclusion that the type locality is Cordón del Portillo, Mendoza province, Argentina, where Darwin collected and briefly characterized a viviparous lizard. Here we provide a re-description of Darwin's specimen and two morphological characters that distinguish it from other populations in Chile and Argentina previously assigned to this species. In November 2009, specimens from the locality where Darwin collected his “viviparous lizard” were collected, confirming the identity of the type. This study also reveals that P. gynechlomus should be considered a junior synonym of P. palluma. Populations of Phymaturus of the palluma group farther to the north, from the Sierra de Uspallata and southern San Juan province, are determined to be different lineages and should be described formally. The name P. adrianae has been applied to the species that occurs in the Sierra de Uspallata, but we show here that it has not been formally named and is therefore a nomen nudum. Chilean populations previously considered to be P. palluma should be described formally.