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