Liolaemus, es el segundo género más diverso dentro de Iguania, con más de 245 especies. Se describe una nueva especie de Liolaemus, perteneciente al subgénero Eulaemus, grupo o sección de Liolaemus montanus. Esta especie habita en un sector cordillerano muy restringido de la Provincia de Salta, Argentina, y en la provincia de Atacama, Chile; siempre por arriba de los 3 600msnm. Este nuevo taxón presenta características de lepidosis y patrón de coloración claramente diferente a los de las demás especies que integran el grupo de L. montanus, se destaca como carácter exclusivo entre todos los Liolaemus, la presencia de poros postcloacales. Este carácter es novedoso, no sólo en el género, sino también en todos los Reptilia, tornándose un descubrimiento morfológico de suma importancia, ya que sólo se conocen para algunos reptiles únicamente poros precloacales y femorales. Con base en las observaciones de campo realizadas, este nuevo Liolaemus es una lagartija relacionada a los ambientes rocosos, que utiliza para refugiarse, es una especie omnívora y los machos son muy agresivos al ser manipulados.
Liolaemus belongs to the Eulaemus subgenus, that is included in the Liolaemus montanus group or section, and is distributed in Argentina, Bolivia, Chile and Peru. The species members of this clade inhabit arid and high altitude environments, usually above 2 800m, and have a strong tendency to herbivory and a viviparous reproductive type. In a herpetological expedition to the Salta Province highlands, Argentina, in April 2012, we collected individuals of this new species for their description. The specimens were collected with loop, slaughtered by anesthesia and deposited in the herpetological collection of Fundación Miguel Lillo in Tucumán (FML). To characterize this new taxon, we analyzed 144 external morphological characters, referring primarily to lepidosis, color pattern, and body proportions, comparing with data from 66 constituent species of the L. montanus group (45 taxa from collection specimens and 21 from literature). Description of the colors in life was made in the field and based on photographs taken during the capture. The species described in this work inhabits a very narrow mountain range area in Salta Province (Argentina), and the Atacama Region (Chile), always above the 3 600m. This new taxon shows characteristics of lepidosis and color patterns clearly different from the other species members of the L. montanus group: the maximum snout-vent length is 72.9mm; shows 74-96 scales around midbody, 89-104 dorsal scales between the occiput and hind limbs, 92-109 ventrals, precloacal pores are evident in both, males and females, and supernumerary pores in males. Also, the presence of postcloacal pores stands out as unique among all Liolaemus. This is a new character, not only for the genus, but also to all Reptilia, becoming a morphological discovery of great importance, since in reptiles only precloacal and femoral pores are known. Based on our field observations, this new Liolaemus is related to rocky environments, which are used as refuge by this omnivorous species, and when handled, very aggressive males.