It is a heavy-bodied, terrestrial crotaline pit viper characterized by its robust morphology and a well-defined triangular head clearly distinguished from the neck. Adult specimens typically reach lengths of 3.9 to 4.9 feet (1.2 to 1.5 meters), with exceptionally large females occasionally exceeding 5.5 feet (1.7 meters). The dorsal coloration pattern is highly diagnostic, consisting of a pale brown, gray, or tan background overlaid with a series of 16 to 27 pairs of dark brown, crescent-shaped, C-shaped, or telephone-receiver-like markings on each side, which are highlighted by sharp white or pale yellow borders. The dorsal surface of the head features a highly conspicuous white or silver cross or anchor-shaped marking that inspires some of its common regional names. This species features loreal pits positioned between the eyes and nostrils for infrared thermoreception, as well as a highly specialized solenoglyphous dentition with long, erectile fangs designed to inject a potent hemotoxic and proteolytic venom.

Geographical distribution: This snake is widely distributed across central and southern South America. Its geographic range encompasses southeastern Brazil (including the states of Minas Gerais, São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul), the entirety of Uruguay, central and eastern Paraguay, and northern to central Argentina, extending south to the provinces of Buenos Aires, La Pampa, Córdoba, San Luis, and Mendoza.

Habitat: It primarily inhabits humid temperate and subtropical ecosystems, showing a strong preference for ecotones bordering wetlands. It is frequently observed in marshes, swamps, riparian forests, damp grasslands, and low-lying flooded savannas. It is also highly adaptable to anthropogenically altered landscapes, utilizing agricultural monocultures such as sugarcane or rice fields, cattle pastures, and rocky hillsides with dense vegetative cover.

Feeding: It is an ambush predator whose diet consists almost exclusively of small mammals, exhibiting a marked specialization toward rodents. Its primary prey items include wild guinea pigs of the genus Cavia (commonly known as apereás), field mice, and marsh rats. It utilizes its highly sensitive heat-sensing loreal pits to locate homeothermic prey in complete darkness, delivering a swift, envenomating strike before tracking the scent of the dying prey using its bifurcated tongue and vomeronasal organ.

Behavior: This species displays predominantly crepuscular and nocturnal activity patterns, spending the daylight hours concealed under fallen logs, thick leaf litter, or rocky crevices to avoid extreme temperatures. While normally slow-moving and reliant on its excellent cryptic coloration to evade detection, it becomes highly defensive when cornered, coiling its body into an "S" shape, rapidly vibrating its tail against the ground to produce a warning rustle, and executing extremely fast, defensive strikes.

Reproduction: It exhibits a viviparous (ovoviviparous) reproductive strategy, with females retaining and nourishing the developing embryos internally rather than laying shelled eggs. Mating cycles are highly seasonal, typically occurring in spring or autumn. Following a prolonged gestation period, the female gives birth to live litters of 10 to 25 neonates, although exceptionally large individuals can produce clutches of up to 40 offspring. The newborns measure approximately 8.6 to 9.8 inches (22 to 25 centimeters) at birth and are fully independent and venomous from day one.

Conservation status: It is not globally classified as threatened, generally considered of least concern because of its extensive geographical range and generalist ecological tolerance. However, localized populations face persistent threats due to habitat loss, fragmentation, and degradation caused by agricultural expansion and cattle ranching, alongside systematic eradication by humans who perceive its venomous nature as a direct threat.