The Liolaemid genus Phymaturus is a clade of saxicolous lizards with 44 species recognized, grouped in the Phymaturus palluma and the Phymaturus patagonicus groups. The chromosome data about this genus are extremely scarce; however, unpublished evidence suggests a great karyotypic diversity, mainly in the P. palluma group. In this work, we describe the karyotypes of six species of the P. palluma group (one of them unnamed) and report a multiple chromosome sex determination system with heterogametic males (X₁X₁X₂X₂ / X₁X₂Y). This sex-system represents a putative synapomorphy for the group. In accordance with the published literature and data obtained in this study, we report a wide variability for the diploid number of the P. palluma group (2N = 26 to 36) but same autosomic fundamental number in all the species of the clade (FNa = 32). Such variation is a consequence of different numbers of telocentric macroautosome pairs among karyotypes (2 to 10), suggesting chromosomal evolution of the group, driven mainly by successive Robertsonian rearrangements.