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Re: Venom in Sinornithosaurus



Damn, swore I wouldn't this on Christmas Day. Oh well, what the heck...

Could be just a matter of time and chance. I stress I have no clue what is 
known about relative ages in the geo-record. 

The picture I am getting, especially from Pinsdorf's post, is that of a large 
group of snakes that seems to range (among species) from mere incipient venom 
production (minus any delivery system) to more highly evolved delivery systems 
and more complicated toxins. In other words, each representing various stages 
of a common process, perhaps post-diversification morphological convergences 
overlying a common ancestral ability to produce a specific type of venom. 
Co-existing "transitional species" as it were. 

I suppose there could be a 'basal prey' that set the 'template', as well...

Or not. But they do seem rather "unfinished" when compared to the incredible 
specializations of rattlesnakes. 

But there again, crotalid venom is apparently highly malleable both w/in and 
among species, so you are be quite right to look for or even predict functional 
'channeling' relative to the focus on anticoags.

Heh. the devil makes me write this: are you absolutely sure the anticoag focus 
is really there? Because I am strictly taking your word for it... }:D

Long post, chopped text likely...

--- On Fri, 12/25/09, Mike Habib <habib@jhmi.edu> wrote:

> From: Mike Habib <habib@jhmi.edu>
> Subject: Re: Venom in Sinornithosaurus
> To: d_ohmes@yahoo.com
> Cc: dinosaur@usc.edu
> Date: Friday, December 25, 2009, 3:41 PM
> Excellent point; there is indeed the
> digestive angle.  My followup question on that would
> be, however: what is it about rear-fanged morphology (or
> other aspects of the physiology of snakes carrying
> rear-fanged apparatus) that makes anticoagulation breakdown
> especially helpful?  The widely cytolytic venoms used
> by many viperids (and quite a few elapids, actually, despite
> what you often hear) seems to do some serious pre-digestion
> - the flesh literally starts to fall off of a prey animal
> injected with such toxi
lone has less of an obvious digestive
> function. But just because it's less obvious doesn't mean
> it's wrong - it just raises more questions, is all.
> 
> Cheers,
> 
> --Mike Habib
> 
> 
> Michael Habib
> Assistant Professor of Biology
> Chatham University
> Woodland Road, Pittsburgh PA  15232
> Buhl Hall, Room 226A
> mhabib@chatham.edu
> (443) 280-0181
> 
> 
> 
> On Dec 25, 2009, at 1:46 PM, don ohmes wrote:
> 
> > Well, there is the digestive angle...
> > 
> > --- On Fri, 12/25/09, Mike Habib <habib@jhmi.edu>
> wrote:
> >> 
> >> Rear-fanged colubrids are actually quite
> widespread, both
> >> phylogenetically and geographically.  Only a
> handful
> >> have venom that is medically significant to
> humans, but the
> >> few that do really pack a wallop (twig snake,
> boomslang, a
> >> few others).  Interestingly, despite the
> convergent
> >> nature of opisthoglyphy in the various venomous
> colubrid
> >> groups, many (most?) of them seem to share a
> tendency to
> >> utilize blood vessel wall damage and anticoagulant
> effects
> >> as a primary attack form.  Very few, if any,
> are
> >> substantially neurotoxic.  Human fatalities
> from
> >> boomslang bites, for example, occur as a result of
> massive
> >> internal bleeding.  Even those species that
> have little
> >> effect on humans and are not considered
> "medically
> >> significant" seem to produce somewhat accelerated
> bleeding
> >> from the bit wound.  To the best of my
> knowledge, no
> >> one has determined a functional, phylogenetic, or
> >> developmental underpinning to this trend (but
> someone else
> >> here may know something I don't).
> >> 
> >> Cheers,
> >> 
> >> --Mike Habib
> >> 
> >> 
> >> Michael Habib
> >> Assistant Professor of Biology
> >> Chatham University
> >> Woodland Road, Pittsburgh PA  15232
> >> Buhl Hall, Room 226A
> >> mhabib@chatha
> > 
> >> (443) 280-0181
> >> 
> >> 
> >> 
> >> 
> 
>