I think Ptyas carinatus is the longest colubrid species. I've heard of specimens over twelve feet in length, and not too uncommonly either. I wouldn't be surprised if there were a few accounts of specimens up to fifteen feet long. It should be recognized too, that they are consideredOphiophagus mimics, which as we all know, are the longest venomous snake species. Perhaps, there is a connection there.
On the other hand, if carinatus has never been known to attain lengths of fourteen feet or more Spilotes would have to hold the record, as there are well documented examples of fourteen foot Spilotes pullatus. Undoubtedly, carinatus attains the greatest lengths on average.
After those two, I think Pseustes sulphureus could come in third. Eleven foot examples are known to exist, and perhaps they could grow even larger.
Orthriophis sp., or Boiga cynodon may be fourth. I know for a fact that cynodon is the longest of the Boiga, and I remember an account of a twelve foot specimen - though I doubt its validity.

So that's my .02, I hope it provides some more insight.
-----
Roy Blodgett
Green Man Herpetoculture
royreptile@yahoo.com

1.1 Drymarchon corais
2.2 Pseustes sulphureus
1.1 Pseustes poecilonotus poecilonotus
1.1 Lystrophis pulcher
1.1 Lampropeltis getula californiae (desert phase)
1.1 Boiga dendrophila dendrophila
2.3 Pogona vitticeps (snow and red/gold)
1.0 Iguana iguana

“All men lie enveloped in whale-lines. All are born with halters round their necks; but it is only when caught in the swift, sudden turn of death, that mortals realize the silent, subtle, ever-present perils of life.”- Herman Melville

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• On average.... - tokaysrnice, Thu May 22 20:44:17 2008
• edit.. longest - tokaysrnice, Thu May 22 20:46:00 2008
• RE: On average.... - Royreptile, Thu May 22 21:07:46 2008
• RE: On average.... - dan felice, Fri May 23 03:49:59 2008
• RE: On average.... - tokaysrnice, Fri May 23 09:28:22 2008
• RE: On average.... - Oxyrhopus, Fri May 23 08:04:06 2008
• RE: On average.... - tokaysrnice, Fri May 23 09:25:18 2008
• RE: On average.... - dan felice, Sat May 24 04:39:59 2008