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RE: Venom in Sinornithosaurus



Michael Erickson wrote-

> Regarding the "teeth just slipped out of their sockets" thing, this is likely 
> incorrect. There are several specimens of *Sinornithosaurus* that preserve 
> the very same elongation of the teeth, and always maxillary teeth 8 - 11. 
> Some rather incredible coincidence.

I haven't read the paper, but the only other described specimen of 
Sinornithosaurus I know of is the S. haoiana holotype, which has four 
articulated teeth, one of which is in the same position as the long ones of S. 
millenii but much shorter (the others are alsao shorter).  This is of course 
because it's still fully inside its socket.  It also has at least two 
completely disarticulated teeth preserved by the maxilla and dentary, showing 
disarticulation is easy in this taxon.  The undescribed specimens I've seen 
lack elongate maxillary teeth as well.

> Note that although many non-venomous extant taxa do indeed possess grooved 
> teeth, the presence of grooved *rear* teeth has never, ever been documented 
> in any non-venomous animal, as Brian Fry has noted. It is especially 
> suspicious that only the longest, sharpest, and most "fang-like" teeth have 
> grooves.

This is untrue.  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 (both lingually and 
labially).  It would be quite odd for any venom system to both lingually and 
labially enter the teeth, even ignoring all the other objections.  Note the 
dentary has no associated "venom gland fossa" nor a canal leading to the tooth 
row from the external surface.

> 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.

> What I think we need to be doing is celebrating a truly amazing new 
> discovery, or at the very least contemplating what sort of implications this 
> would have if true. We should not be so closed-minded, leaning back in our 
> chairs trying to figure out how to "reinterpret" or dismiss the evidence. 
> Something we should definitely avoid is an ad hominem attack on the paper - 
> i.e. casting immediate doubt on it simply because a BANDit (Martin) happens 
> to be involved. I honestly believe that the authors have done a fantastic job 
> of supporting their case*, but even if they didn't, the burdon of proof does 
> not automatically lie with the "new" or "radical" theory/hypothesis anyway; 
> rather, it lies with *us* to demonstrate that the "traditional" or "widely 
> accepted" view is well-supported enough as to not be challenged. Often, 
> nearly universally accepted ideas (the ectothermic and featherless dinosaurs 
> of the majority of the last century, for example) in reality have little to 
> no factual basis, or are based merely on an absence of contrary evidence. The 
> burden did not lie on those such as Ostrom and Bakker who were advocating 
> endothermic (or even feathered) coelurosaurs; the burden was on those who 
> maintained ectothermic and scaly coelurosaurs to demonstrate that the 
> classical view was was the correct one, or that it was at least based on 
> *something*. They failed to do this, and the enormous mountain of data that 
> has accumulated since has demonstrated beyond any reasonable doubt that 
> Ostrom and Bakker were correct. Perhaps this conclusion could have been 
> reached even sooner, and thus the science could have progressed even farther 
> than it has now, had folks not been so dead-set against such notions for the 
> first few years fallowing their initial proposal and used up so much time 
> trying to prove these "crazy new ideas" wrong, a task at which they did not 
> succeed in any case.

The burden of proof actually DOES lie with those claiming Sinornithosaurus was 
venomous, as phylogenetic bracketing gives the default state for any dinosaur 
as unvenomous.  Feathered coelurosaurs were different, as at the time they were 
between scaled sauropodomorphs and feathered avialans, making feathers 
ambiguous.  Same with endothermic dinosaurs, being between ectothermic 
crocodilians and endothermic avians.  As much as I love disproving the MANIACs, 
I would accept a hypothesis of theirs if it was supported by the data.  It's 
just that they so rarely are (after some thought, Martin might have been right 
about Archaeopteryx lacking interdental plates; so there's one exception).  
Note these are not ad hominem attacks, as I always support my counterarguments 
with data as opposed to claiming MANIACs are wrong about everything because 
they are wrong about bird origins.
 
Mickey Mortimer
The Theropod Database- http://home.comcast.net/~eoraptor/Home.html