Secrets of the Rarest Venom

In the summer of 1949, William Burger and his brother Jack were in the mountains of southern México collecting specimens for William's graduate work at the Univeristy of Illinois. On the 22^nd of July, on an otherwise unremarkable hill in southern Oaxaca, they unknowingly made the find of a lifetime when they happened upon a horned pitviper.

While superficially similar to Ophryacus undulatus, a handful of differences caught Hobart Smith's trained eye. Like a few other pitviper species in Mexico, this specimen had horn-like projections above the eyes, but these were distinctly wide, wedge-shaped horns. There were also fewer scales between the eyes and on the underside of the tail. With these differences, Smith described Burger’s specimen as the new species: Bothrops sphenophrys and inferred a close relationship to B. undulatus some eleven years after the Burger brothers first picked the snake out of the cloud-forests in Oaxaca.

William Leslie Burger's unique pitviper from Oaxaca

Fast forward to 1971. Without public explanation, W. Leslie Burger placed the species in synonymy with Ophryacus undulatus in his PhD dissertation at the University of Kansas. 18 years later, Campbell and Lamar followed his lead, but this time noting that most of the distinguishing characters for O. sphenophrys fall within the range of known variation for O. undulatus in their book on The Venomous Reptiles of Latin America.

Unbeknownst to all parties, this “variation” was contaminated by a third, undescribed species of horned viper. HERP.MX's chance encounter with that third species in 2010 and a subsequent review of museum specimens resulted in the description of Ophryacus smaragdinus and validated Hobart Smith's half-a-century-old Ophryacus sphenophrys.