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Re: [svp notes and other stuff]

Nick Longrich <nrlongri@midway.uchicago.edu> wrote:
> --Some SVP notes--

*All kinds of interesting dino info snipped*

> Venomous theropods?
> Don't reject this out of hand, it's a very, very weird tooth. It
> has to be seen to be believed. Instead of denticles it's got a series of
> pits on the carinae, towards the distal end of the tooth these pits > joined
together into a groove. Really weird, it pretty much blew away 
> all the people who looked at it. One supposes that the grooves might be
useful for venom transport (as was suggested at the meeting), say from the
saliva although if there were actual glands you'd expect the grooves to extend
farther down, wouldn't you?


Yes and no, if this was an early stage of evolution of venom in theropods then
this could be feasible (of course no one ever said that evolution had to be
perfect either). Heck we have snakes alive today that have no grooves in their
teeth, yet contain venom (colubrids mostly). The venom runs out and down pits
on or near the teeth, effectively saturating the maxillae (and I thought
excessive drool was bad). The owner of that tooth sounds like it might be one
step "up" from that.


> Another interesting thought- what if these pits served to collect bits  > of
flesh, bacteria, morning mouth and general nastiness to inflict into >
whatever hapless animal the thing bit into, as has frequently been      >
suggested for theropods here and elsewhere, a strategy apparently       >
employed by the Komodo dragon. 


Note: Although it is possible that chunks of meat can get stuck in the teeth
of Komodo dragons and even though it is widely popularized, I know of no
evidence of these pieces ever being found in a live specimen. In Auffenberg's
infamous study of the ora he too found no evidence for this. For the most part
the bacteria seemed to get their nutrients from the blood that comes out of
the gums as the serrated teeth erupted through them. So the idea of a room
temperature meat locker is still up in the air.


*Interesting KGB history snipped*

> Anyways what bugs me about the Morning Mouth of Death Theory is
> that not much actually does this. Predators that inject venom include
> shrews, snakes, spiders, octopi, gila monsters, scorpions, wasps, and > cone
shells, platypi inject it defensively with spurs and then various > things
like toads and frogs have skin toxins, some millipedes use > cyanide (which
gives them that lovely almond smell), and there are even > birds with skin
poisons if I am recalling a recent Jared Diamond article > correctly. Not much
is known besides the Komodo that uses bacteria. Why > is this? 


Lynx are apparently known to have "poisonous" bites as well.


> The one difference I can think of is that  the Komodo is going after big >
prey, this may make this strategy feasible. For one thing, it might take > a
lot of venom to bring down big animals; this may make it difficult to > inject
enough to reliably subdue the animal and expensive to produce a > lot. The
cool thing about using bacteria as your toxin is that unlike > venom molecules
the little suckers are self-replicating. You just need > to get a little in
and they reproduce until there is enough to kill the > animal. The other thing
is that the venoms of most predators are used to > rapidly subdue prey to
prevent it from escaping. This just might be > really difficult with large
animals- consider that even a substance as > lethal as rattlesnake venom might
take something like an hour to start > affecting an animal as large as a
human, and I assume it's even harder > to subdue, say, a cow-sized young
duckbill. So maybe venom doesn't > really have an advantage over bacteria as a
toxin when you are subduing > large animals, since in either case it is going
to take a while to > subdue them.


An interesting thought, but even Komodos don't rely on their bacteria laden
mouths to subdue prey (large or otherwise). In almost all cases, oras just
come up and tear into the animal. Anything up to about goat size can be killed
on the spot (usually by grabbing the neck and thrashing away) while animal
such as Samba deer and water buffalo get their achilles tendon slashed. I
think the reason for all those different bacteria in ora mouths might be more
related to symbiosis with a heavy bias towards the bacteria. With the heavily
gum lined mouth of Komodo dragons coupled with their excessive saliva (an
adaptation to handling swallowing extremely large chunks of food) and serrated
teeth that have to come up out of that lining, these bacteria are left with
this wonderful little environment that is perfect for them to thrive in. The
only benefit the dragons get is a slightly higher success ratio for prey that
"get away."

In regards to venom, a strange thing about reptile venom is that in many cases
it is way too strong for its own good. 

For instance, the inland Taipan (_Oxyuranus microlepidotus_) injects its
rodent prey with enough venom to kill two hundred thousand mice.

Such extremely potent venom delivered in such exaggerated doses seems kinda
nutty, unless perhaps the ancestors of the Taipan and other venomous snakes,
were hunting much larger prey. 

That or perhaps because there is no apparent selective disadvantage to having
more potent venom.

Just some passing thoughts. 

One must also consider the venom type. If these possible venomous theropod had
a predominantly neurotoxic venom then it would need much smaller doses to
subdue its prey than if it used predominantly hemotoxic venom.

Incidentally did they mention wether or not this tooth was maxillary or
dentary? It would be interesting to see which direction this proposed venom
was flowing in.


Jurassosaurus's Reptipage: A page devoted to the study of and education on,
the reptilia:


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