The number of species of the genus Phymaturus has increased consistently since 1995, when only 10 species had been described. Over the last two decades, this number has risen to 46. This group of lizards is characterized by a flattened body and spiny tail; they are viviparous and herbivorous and inhabit rocky regions, using crevices as refuges. For the present study, an integrative taxonomy approach was used with the aim of rigorously assessing the taxonomic status of a population occupying the Auca Mahuida volcanic field. Evidence from genetics, morphology, and biogeography suggests that this population is a separate lineage from all described species. This new species can be distinguished from close relatives by a longitudinal white dorsal line along the midline at the base of the tail. Special emphasis was put on determining if this taxon presented differences from the nearest relatives of the palluma group: P. roigorum and P. tromen. Consistent differences were found.