>>aglyphous, opisthoglyphous, and so forth
>>
These terms are pretty meaningless when applied to the dramatic dentition diversity that is present across the myriad of snakes. Exactly the variation that would be expected.
>>I will accept Dr. Fry's work that Duvernoy's is outdated and the gland is no different that any other venom gland, but what is the tooth structure of Thamnophis? I can't really find a source that says for sure. I recently had a garter snake die and I wanted to try and examine this for myself, but I have not thought up the best method of examining this little fella. I would also rather ask someone who already knows because I don't want to take him out of my freezer since his necropsy cleaned out 3 cans of air freshener in attempt to cover the terrible smell.
>>
Good question. I haven't observed their teeth but have played with a variety of related snakes in the Natricidae family. Some of which (e.g. Macropisthodon) have massive fangs, others (such as Sinonatrix) have minimally enlarged teeth. I would suspected that Thamnophis are more towards the minimal end. However, all they need to do is puncture the skin in order to deliver the small amounts of venom. Feeding on soft skinned amphibians makes this a pretty trivial job.
>>I also found sources calling Lampropeltis, Elaphe, Pantherophis, etc "rear-fanged." Now I thought these were the colubrids which were accepted as the few "non-venomous" snakes that have evolved to a mucus secretion.
You are correct. The American clade of Arizona/Lampropeltis/Pantherophis/Pituophis/etc. lack a protein secreting gland, putting out mucus instead. It appears that some Asian relatives (e.g. E. carinata and E. mandarinus) also have only mucus secreting glands but we haven't finished this work yet and there may be other Elaphe types in Asia/Europe also having only a mucus secreting gland. Whether or not this happened independently and represents a parallel loss, or if one of these snakes was the ancestor of the N. American snakes is something we are working to resolve. The evidence seems to be pointing that the Asian Elaphe types are also lacking in the venom gland. I'm referring to the true ratsnake types (such as cave racers, mandarin rats, etc.) as opposed to animals like radiata which it turns out is actually much more closely related to racers than to ratsnakes.
The fact that the taxonomical mess of these animals is slowly being resolved will allow for a mapping of the evolution of venom and the secondary loss in some lineages. As a parenthetical aside, loss of venom is something that has already been documented three times in Australian elapids: the marbled sea snakes (Aipysurus eydouxii) and the turtle headed sea snakes (Emydocephalus genus) independently switched to a diet specialising on fish eggs, followed by a breakdown in the venom delivery apparatus and the collapse of the toxicity of the venom. Below are links to two papers by us on it. Some species of the Australian shovel-nosed snakes (Brachyurophis) specialise in feeding on lizard eggs and we are investigating how this has changed the venom delivery and venom itself. It appears to be a similar situation to the sea snakes.
http://www.venomdoc.com/downloads/2005_BGF_Aipysurus_eydouxii_3FTx.pdf
http://www.venomdoc.com/downloads/2005_BGF_Aipysurus_eydouxii_PLA2.pdf
>Or am I off here? Certainly if they are not accepted as venomous (having venom glands) they would not have enlarged rear fangs or grooves to channel a venom.
>>
Enlarged teeth are not a prerequisite (which is why the dentition classifications are meaningless).
>>Along with this, where does Drymarchon sit?
>>
Drymarachon, by contrast do have a venom secreting gland.
Good questions 
Cheers
Bryan
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Dr. Bryan Grieg Fry
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Australian Venom Research Unit,
University of Melbourne
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Population and Evolutionary Genetics Unit,
Museum Victoria
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http://www.venomdoc.com
