The difference between difference between types of snakes

[MarkS]

Sidenote/question: Aren't some venomous snakes considered colubrids?

Yes, there are many rear-fanged venomous snakes that are colubrids. I believe the main difference between Elapids and Vipers is that the Elapids have fixed fangs and the Vipers fangs fold back.

There are somewhere around 18 or so families of snakes depending on which taxonimist you talk to.