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Re: More Dino Venom



> 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.

And indeed, it would be the most parsimonious conclusion _in the absence of morphological evidence for venom_. Gong et al. understand this full well, and have therefore tried to provide exactly such evidence. The argument here is that they failed.

> 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.

Gong et al. are the ones who are reinterpreting the morphology of *Sinornithosaurus* here... :-)

>> 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.

Never use words like "doubtless" or "for all to see" about a grainy photo. The photo you linked to is way too small to test any such claims.

For instance, I have no qualms about suggesting that the "bar" is actually the formerly flat and now deformed left maxilla lying _on top of_ a bone which could be a palate bone or two (palatines, pterygoids...). Note how it appears to continue forward way beyond where it meets the toothrow. Alternatively, it could be the right maxilla. There's a tooth between the toothrow and the nostril -- it must lie on the other side.

Without having seen either the specimen (through a microscope!) or at least one color photo twice the linear dimensions of my screen (and thus much bigger than the fossil itself), preferably several from different angles and under different lighting, I'm not going to use expressions like "without question".

 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.

Both of these facts are contrary to what I'd expect for a venom delivery system.

 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.

Parsimony is not about absolute levels of confidence. It's about relative ones.