Re: Venom in Sinornithosaurus

[Mike Habib <habib@jhmi.edu>]

On Dec 25, 2009, at 12:32 AM, Michelle Pinsdorf wrote:

> To your credit, most people, especially in the pet trade, would say  
> most colubrids are not venomous. As far as I know corns aren't  
> venomous at all, anyway. But the venom that Thamnophis species  
> produce is literally chewed into prey, they really have to gnaw on  
> you to get it in, and even then only a handful of people experience  
> a reaction to it. I would think a neurotoxin that mild wouldn't do  
> anything much to kill prey, but serve better to disable it or reduce  
> struggling while being swallowed.

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@chatham.edu
(443) 280-0181