[3] Although the heat-sensing pits that characterize the Crotalinae are clearly lacking in the viperines, a supernasal sac with sensory function has been described in a number of species.

This sac is an invagination of the skin between the supranasal and nasal scales and is connected to the ophthalmic branch of the trigeminal nerve.

Experiments have shown that strikes are not only guided by visual and chemical cues, but also by heat, with warmer targets being struck more frequently than colder ones.

[5] Generally, members of this subfamily are ovoviviparous, although a few, such as Pseudocerastes, Cerastes, and some Echis species are oviparous (egg-laying).

However, they were eventually considered so distinctive within the Viperidae, that separate subfamilies were created for them:[1] Nevertheless, these groups, together with the genera currently recognized as belonging to the Viperinae, are still often referred to collectively as the true vipers.