Re: Vampire-osaurs?

[Eric Hall <Hall966@msn.com>]

Are there any theories on how hollow teeth (or spines) and venom sacs 
evolved?  I myself can't come up with the vaguest notion how this might have 
happened, in any animal.

Eric Hall


----- Original Message ----- 
From: "Michael Habib" <mbh3q@virginia.edu>
To: <ajgrant@eastlink.ca>; <dinosaur@usc.edu>
Sent: Tuesday, July 06, 2004 11:38 PM
Subject: Re: Vampire-osaurs?


> >> ... More
> >> to the point, however, they would have to be grooved or hollow to
> >> inject a
> >> toxin, which may or may not be evident from the specimens.
> >
> > IF it needed to be injected. I'm pretty sure there are frogs/toads that
> > can secret a poisonous substance when the need arises.
>
> Yes, many amphibians can.  However, they have permeable skins, and this
> relates to secretion.  No squamate reptiles secrete toxins across the skin
> (as far as I can recall), and no extant archosaurs other than the one bird
> exception noted on the list (thanks for that guys) do so.
>
> >> Thus, extant archosaurs are not prone to be
> >> poison
> >> users, and none are venomous.  Overall, reptiles get a reputation as
> >> toxin
> >> users only because snakes are prone to evolving venom use.  Their
> >> unique
> >> ecology and physiology plays a major role in this.
> >
> > Also, komodo dragons are technically poisonous.  And I believe that sea
> > snakes have some of the most toxic venom among snakes. They'd rather
> > not go chasing their prey all through the water until the venom takes
> > full effect, go following it's scent through the water and/or give
> > another predator a free meal. Mosa/Plio/Plesio, anybody? hehehe . . .
> >
>
> Komodo dragons are _technically_ not poisonous.  They have highly 
> infectious
> wounds, and the Staph infections resulting produce their own toxins.  No
> extant Varanus species injects venom.
>
> True, sea snakes have neuroinhibitors that act rapidly, as do cone snails
> and several fish.  So, marine piscavores may have a greater chance of
> deriving venom use.  Might be worth looking into to see if any extinct
> marine taxa have left signs of venom use (anyone out there have a ref or
> two?).  From an extant bracketing point of view, which is granted somewhat
> circumstantial, Mosasaurs would be the best candidate.
>
> Cheers,
> --Mike Habib
>
>