A picture of the of Stegonotus cucullatus (Slaty-grey snake) showing how much more vascularised the tissue is aroudn the larger back teeth are in this species, evidence of active use of the venom.
A huge amount of my time is spent examing the molecular evolution of the venom in the various families of snakes that are considered 'colubrids'. These snakes were formerly dumped into one vast family called the Colubridae. However this family is not a natural group and actually seven or more families that are in some cases far far more closely related to elapids than they are to other 'colubrids'.
The venoms of these snakes are in some cases just as complex as elapids and vipers. The venoms are exactly that, true venoms. They are not 'toxic saliva'. The gland producing the venoms was formerly referred to as the 'Duvernoy's gland'. However, this is an artificial term that is evolutionarily misleading, it is in fact the same venom gland as the one found in cobras and rattlesnakes. This is because venom evolved once, at the very base of the Colubroidea (Advanced snakes) evolutionarily tree, long before any of the 'colubrids' evolved. Thus, these snakes have the same gland and produce some of the same toxins. We even pulled out the classic cobratoxin (a 3FTx (three-finger toxin)) from a bloody ratsnake!! The toxin was homologous to and just as potent as a comparative cobra toxin. Same toxins = same gland.
In the same vein, the distinction between opisthoglyphous (rear-fanged) and aglyphous (lacking fangs) "colubrids" has been abandoned. Not only did this distinction shoehorn a wide variety of dentitional types into two artificial, non-monophyletic categories, but it similarly ignored the fact that a wide variety of "colubrids" possess complex venoms, with widely shared toxin gene families that transcend any divisions based on dentition types.
