Exhibits a robust, moderately sized body for its genus, with a snout-vent length measuring between 55 and 68 millimeters in mature adults. The head is triangular and clearly demarcated from the neck, covered with rough, overlapping cephalic scales. Its dorsal coloration is predominantly olive-brown or grayish, uniquely patterned with a series of dark, paired transverse markings that evoke shadows, which inspired its scientific name. The flanks present lighter hues with subtle yellow or orange highlights in breeding males, while the venter is pale gray or off-white, often speckled with fine dark spots. The tail is exceptionally strong, exceeding the length of the body, and is covered with keeled scales arranged in tight, concentric whorls.

Geographical distribution: Is strictly endemic to the northwestern region of Argentina. Its known populations are localized primarily within the Catamarca province, with notable records in the Belén department, the western slopes of the Sierra de Belén, and surrounding areas of the archaeological site of El Shincal. This highly restricted geographic range confines the species to intermontane valleys and pre-Andean slopes, spanning altitudes between 1,200 and 2,500 meters above sea level.

Habitat: Thrives in arid and semi-arid landscapes characteristic of the Monte de sierras y bolsones phytogeographic province and its transition into the Prepuna. It is closely associated with rocky substrates, stony scree slopes with sparse vegetation, and gravelly alluvial plains. The dominant flora in its habitat consists of xerophytic shrubs such as Larrea, Fabiana, and Gochnatia, along with various cacti species. This vegetation provides essential thermal refuges and shelter from the extreme daily temperature fluctuations of high-altitude deserts.

Feeding: Sustains an opportunistic insectivorous diet, actively foraging for seasonally abundant arthropods within its harsh environment. It preys primarily on coleopterans, formicids, orthopterans, and various insect larvae. Additionally, it may occasionally consume small arachnids and, as a facultative strategy, ingest plant matter such as tender buds, flowers, or seeds to supplement its hydration during periods of severe drought.

Behavior: Displays strictly diurnal and strongly heliothermic habits. It initiates its daily activities by basking on sun-exposed rocks early in the morning to rapidly raise its core body temperature. Highly agile and wary, this reptile relies on speed and cryptic coloration that blends with rocks and sandy soils to evade predators. When threatened, it darts quickly into deep rock crevices or hides beneath dry leaf litter and thorny shrubs. Males are highly territorial, performing rhythmic head-bobs and throat displays to signal dominance to rivals and attract females.

Reproduction: Follows an oviparous reproductive strategy, setting it apart from high-altitude congeners that exhibit viviparity. The mating season is highly seasonal, triggered by rising temperatures in late spring and early summer. Following successful courtship, females deposit a single annual clutch containing between 2 and 5 flexible-shelled eggs. These are carefully buried in shallow underground chambers dug in moist, sandy soil beneath flat rocks, which function as natural thermal incubators by absorbing and retaining solar heat.

Conservation status: Is currently categorized at the national level in Argentina as Not Threatened, though some herpetologists regard it as Data Deficient due to the scarcity of comprehensive population studies. Because of its restricted distribution, its populations are highly vulnerable to localized habitat loss. Primary threats include overgrazing by livestock, which degrades essential shrub cover, and soil disturbance caused by road construction and small-scale mining activities in its native range.