Some of the hypotheses of relationships among snakes can be found if you scroll down to the older messages in this forum. Other hypotheses of relationships are often buried within the pages of scientific journals, although sometimes these articles are made available by the authors on the world wide web. An important thing to remember is that these hypotheses are by no means established scientitic truth. They are subject to constant revision as scientists find better characters with which to analyze relationships.

Phylogenetic history cannot be directly observed, as George Gaylord Simpson pointed out, and must be inferred from the available evidence, some of which is not directly phylogenetic. For example, some scientists have attempted to infer phylogenetic relationships from dietary preference, even though diet is often strongly influenced by the availability of prey species and may differ geographically within a species' range. For now, there is no general consensus concerning phyletic relationships among animals. This is because the character evidence used by many scientists are often subject to convergence or parallelism. Scientific theories are only as good as the evidence that support them. For now, the quest for better character evidence will continue.

Molecular evidence tends to be superior to morphological characters in general, but even molecular data often disagree with each other. In the case of the origin of whales and the relationships among their relatives, the artiodactyls, the use of SINE characters have shown great promise. If similar sorts of characters can be found in snakes, then there is a strong possibility that a robust theory of snake relationships will emerge. For now, do not treat any single hypothesis or diagram of relationship as absolute truth, although there are agreements among scientists on some subsets of relationships. It is generally agreed that the lampropeltine genera such as Pituophis, Arizona, Bogertophis, Stilosoma, Cemophora and Lampropeltis are descended from a species of Elaphe which originated in the Old World. It is also generally agreed that the "advanced snakes" of the family Viperidae, Elapidae and Colubridae are all descended from a single common ancestor. Relationships that are more specific than these tend to be controversial as scientists are still attempting to work out the branching orders among the living snakes, often by using less than ideal characters.

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