Phymaturus mallimaccii, also known commonly as the thorntail mountain lizard, is a species of lizard in the family Liolaemidae. The species is endemic to Argentina.

Etymology: The specific name, mallimaccii, is in honor of Argentinian geologist Hugo Salvador Mallimacci.

Distribution: Phymaturus mallimaccii is found in the Sierra de Famatina, La Rioja Province, Argentina.

Habitat: The preferred natural habitat of Phymaturus mallimaccii is grassland, at altitudes of .

Behavior: Phymaturus mallimaccii is terrestrial and saxicolous (rock-dwelling).

Diet: A herbivorous species, Phymaturus mallimaccii eats flowers, especially those of the genera Hypochoeris and Werneria.

Reproduction: The mode of reproduction of Phymaturus mallimaccii has been described as viviparous and as ovoviviparous.

Taxonomy: Phymaturus mallimaccii is a member of the Phymaturus palluma species group.