Shane is right. All elapids, period, are front, mostly fixed fanged snakes. I say mostly fixed, because most don't have the mobility that viperids do with their 'hinged' fangs, though some, like Acanthopis (death adders) have a large degree of mobility. I'm assuming you got your information on elapids being rear-fanged from our coral snakes? If I'm wrong, I apologize. It's a widely perpetuated myth that corals are rear-fanged, when in fact, they are just as front-fanged as any cobra, etc.
As for real rear-fanged snakes, of which all happen to be colubrids, there is a HUGE amount of variation between dentition. You have some, like hognoses, with fairly primitive enlarged rear teeth. Then you have others, like boomslangs, with relatively gigantic fangs. Likewise are there gigantic differences in venom composition and toxicity among colubrids. Again, some like hogs are pretty mild. Others, like booms and twig snakes, are known to kill people pretty easily.
Hope this clears up a few things.
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Chance Duncan
www.rivervalleyexotics.com