[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

More Dino Venom



Condensed package of responses...

Erik Boehm wrote:

> I agree, if the platypus/monotremes had gone extinct, we'd have no
>examples of venomous mammals (as far as I know)
>
> And if in a million years there were no snakes, and if a few lizard
>species went extinct, we'd be saying reptiles shouldn't be venomous by that
>logic as well.

Exactly.

>Re-interpreting evidence is always fine with me - I'm glad T-rex's aren't
>depicted in the tripod stance anymore, are you?

Of course I am. Basically my point was that wanting to reinterpret the evidence 
for no reason other than that the hypothesis just seems too "radical", and 
therefore ought to be reinterpreted, is not very scientific. I'm always all for 
reinterpretaion, so long as there is a valid scientific reason for it.

> If I were to claim all theropods had retractable neck frills as depicted
>in Jurassic park on Dilophosaurus, would the burden of proof lie on the
>rest of you to say it is wrong?
>To use a more well known example,
>If I were to assert there is a teacup orbiting the sun, somewhere in
>between Mars and Jupiter, and say the burden of proof lies on you to prove
>me wrong, would you conclude you cannot prove one isn't there, therefore
>you must accept my assertion?

Of course not. That was not my point *at all*. It was all merely a cautionary 
tale - don't assume that the most universally accepted theory/hypothesis is 
correct until it is proven wrong beyond any reasonable doubt; Instead, try to 
figure out what the traditional view is *actually based on*, and look at 
weather the "new and radical" view is perhaps better supported - and it often 
(not by any means always, but often) is. That's it, that's all I meant, nothing 
more.

> We don't need to prove no Theropods had venom,

I agree, and that was not even my point (see above).

>we only need to show the claim that *this particular theropod* had venom is
>not adequately supported.

True, and as far as I'm concerned this has not been done.

>And the venomous teeth being in the middle of the jaw? seems odd to me.I
>think there is a good reason snakes have fangs at the tip.If you want to
>"poke" prey with your teeth, then your teeth should be where mammal
>canines>are, or snake fangs. That this dino's putative poison delivering
>teeth arent at the tip of its mouth, suggests to me that their conclusion
>is invalid.

Well, they're called "rear-fanged snakes" for a reason... :)

http://en.wikipedia.org/wiki/Opisthoglypha#snake_dentition

Michael Mortimer wrote:

>Xu and Wu (2001) show that the last premaxillary and first
>two maxillary teeth have "grooves" too, as does one of the small last
>preserved maxillary teeth, and at least nine of the dentary teeth

Okay. I made a mistake.

>>Also remember that the proposed "venom-gland depression" is actually
>>*below* the antorbital fossa and is separated from it by a thin bar of
>>bone, and so it is not the same structure nor is it a part of that
>>structure.

>Untrue, as shown by Xu and Wu's illustration.

I was basing my statement on the illustration in Gong et al.'s paper, which 
shows a bar of bone seperating the proposed "venom gland fossa" from the 
antorbital fossa. Although I do not have the Xu and Wu paper (will try to find 
it) so that I may compare their illustration to the actual skull, I can do this 
for Gong et al.'s illustration. It matches the skull in this photograph

http://www.wired.com/images_blogs/wiredscience/2009/12/dinofangs2.jpg

and therefore seems accurate. In this specimen, at least, there is without 
question a bar of bone seperating the depression in question from the 
antorbital fossa. It (the seperating bar) *is* there, and it is sitting there 
on the actual fossil for all to see. Therefore, it would appear that this 
"venom gland fossa", whatever the heck it may be, regardless of its funtion, 
even if it is an artifact as some have said, it is not the same as the 
antorbital fossa. Also of worthy attention is that the teeth (pay very close 
attention to the tooth the arrow points at) of this specimen seem to have 
grooves closer the tips, right on what would be the crowns of the teeth had 
these teeth slipped out of their sockets (which I'll admit is possible in the 
holotype at least). Two deep grooves per tooth, one on each side. Especially 
interesting is that these grooves look like "real" grooves, and seem different 
from the more deression-like structures on the teeth in the holotype skull (a 
photo of which Denver Fowler linked to). I. e. they look more like potential 
"venom grooves".

Putting the may details aside for a second, the very basic jist of what I'm 
saying is that while Gong et al.'s claims could certainly have been more 
detailed and were perhaps published prematurely, these alternative explanations 
that are being put forth to explain away the evidence are really no better, and 
a few of them would seem to be false. At this point we are in the situation of 
examining *all* possibilities, and no one possibility seems to be substantially 
more parsimonious than the other (to me at least) at this time. I personally 
feel that the evidence is currently leaning toward Gong et al.'s interpretion.

>The burden of proof actually DOES lie with those claiming Sinornithosaurus
>was venomous,

Ugh. :) See above (in one of my responses to Erik).

>as phylogenetic bracketing gives the default state for any dinosaur as
>unvenomous.

This is true, but again, two extant clades is _*nowhere near*_ large enough a 
sample size to be able to draw anthing more than perhaps some very sketchy and 
wholly preliminary conclusions. As Erik pointed out, if in a few million years 
snakes and many lizards were extinct, phylogenetic bracketing would give the 
default state for any reptile of any sort as non-venomous. We simply cannot say 
with much confidence at this time whether venom is extraordinary for an 
archorsaur or not.

~ Michael                                         
_________________________________________________________________
Hotmail: Trusted email with Microsoft’s powerful SPAM protection.
http://clk.atdmt.com/GBL/go/177141664/direct/01/