It is a group considered to be among the most primitive members of the family Viperidae based on head scalation, oviparity, venom apparatus, and because they have round pupils.

[2] Among the viperids, another unique characteristic of this genus is that several species have venom glands that are not confined to the temporal area as with most vipers, but are exceptionally long and extend well down the neck.

[3] These venom glands, located on either side of the spine, may have a length of up to 10 cm (3.9 in), with long ducts connecting them to the fangs.

Others specimens may raise the anterior part of the body off the ground, flattening the neck and moving forward, tongue extended, like a small cobra.

[9] All Causus species lay eggs (oviparity), which among vipers is considered to be a more primitive trait, though not unique.

Nevertheless, South African polyvalent serum is known to be effective against the venom of at least two species of the genus Causus.

The danger from these snakes should not be underestimated as a bite from a large individual on a small child could potentially be fatal.

Earlier reports of fatalities were based on anecdotal evidence; the species involved likely were not properly identified or the cases were grossly mismanaged.

McDiarmid et al.[1] suggested the consensus among the experts in 1999 was that Causus was basal to all viperids, so deserved a separate subfamily.

However, two more recent molecular phylogenetic studies[4][5] have shown Causus is not only not basal to all viperids, but in fact appears to be nested within the viperines.