How SNAKE got his fangs

"Many advanced snakes use fangs—specialized teeth associated with a venom gland to introduce venom into prey or attacker. Various front- and rear-fanged groups are recognized, according to whether their fangs are positioned anterior (for example cobras and vipers) or posterior (for example grass snakes) in the upper jaw A fundamental controversy in snake evolution is whether or not front and rear fangs share the same evolutionary and developmental origin".

"Our results suggest a new model for the evolution of snake fangs. A posterior subregion of the ancestral tooth-forming epithelium became developmentally uncoupled from the remaining dentition, resulting in posterior and anterior dental laminae that are developmentally independent."

Says PZ Meyers of Pharyngula "The key innovation in snake evolution was a subtle one, an uncoupling of two tooth-generating regions that opened the door to more flexibility in the modification of the jaws. The fang/venom gland complex probably evolved once in the common ancestor of these groups, but the elapids and vipers independently stumbled on a secondary change, the suppression of the anterior region, that allowed the posterior fangs to move forward to make a more effective poison delivery system.

Story Reteller: PZ Meyers of Pharyngula
Evolving snake fangs
Evolutionary origin and development of snake fangs