>>Well, Deg, I think they are only referring to a couple Asian ratsnakes, not North American, like Coelognathus radiatus, the radiated ratsnake. These snakes are a little more archaic and still produce the toxins, I believe, but lack a mechanism for delivering it. There are quite a few rear-fanged species right here in the good 'ol USA. Some snakes, like the hognose, even have fangs that can deliver some toxins. But their venom isn't too potent. Hope I recalled that info correctly.
>>
Coelognathus radiatus is indeed the specific rat snake that he references, but on http://www.venomdoc.com/snake_evolution.html he goes on to say:
"The venom gland was developed right at the very base of this tree, long before any of the 'colubrids' even showed up. Consequently, the vast majority of the advanced snakes are venomous, including most of the snakes typically thought of as non-venomous."
Not that I worry about my little Texas rat biting me, even if my subconcious pulls my hand back pretty darn quick when he strikes. It is, however, curious and interesting as it applies to snake evolution though I don't know whether the venomdoc's opinions are widely accepted or not. He discusses the issue in more detail in his paper at
http://www.venomdoc.com/downloads/2003_BGF_alpha-colubritoxin.pdf
On a similiar evolutionary note, I wonder if tail rattling in rat snakes evolved in a common evolutionary ancestor with rattlesnakes or if it a parallel evolution trait.
deg
