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RE: Sinornithosaurus venom



Great summary, Mike.  The teeth are certainly disarticulated, and as Denver 
noted plenty of other theropods have the same kinds of "grooves" on their tooth 
roots.  For instance, just looking at Currie et al. (1990), Dromaeosaurus 
(figure 8.1 J, M), Saurornitholestes (figure 8.2 G), Troodon (figure 8.3 C, E), 
Richardoestesia (figure 8.4 G, J, K, Q, S) and two digested teeth (figure 8.5 
F, I) have them.  The ironic thing is that these are probably replacement pits 
(as illustrated for an unnamed dromaeosaurid tooth by Currie and Zhao, 1993), 
which Martin (1991) earlier claimed were absent in theropod teeth, which was 
among his proofs birds were not dinosaurs.  Furthermore, you're correct that 
the pitting in their "subfenestral fossa" is no different than elsewhere in the 
antorbital fossa, and that there's no actual boundary between it and the rest 
of the fossa.  Nor is there the posteroventral canal illustrated (Xu and Wu, 
2001).
 
Michael Erickson says we're being biased, but I can't think of a single novel 
anatomical interpretation of Martin's or Burnham's that turned out to be 
correct in theropods.  There's basal birds' upright posture and hypopubic cup, 
Archaeopteryx's acromial-dorsal articulation, mediolaterally jointed fingers 
and lack of a postorbital, Caudipteryx's pygostyle, upside-down ischium and 
opisthopuby.

Mickey Mortimer
The Theropod Database- http://home.comcast.net/~eoraptor/Home.html







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> Date: Wed, 23 Dec 2009 10:25:33 -0800
> From: markpauline@rocketmail.com
> To: dinosaur@usc.edu
> CC: jaseb@amnh.org
> Subject: Sinornithosaurus venom
>
> The Gong et al. PNAS paper "The birdlike raptor Sinornithosaurus was 
> venomous" is weakened by unsupported speculation. The authors could have 
> strengthened the paper by quantifying their judgments, making more extensive 
> comparisons with other taxa, and addressing obvious alternatives to their 
> interpretations.
>
> 1) Type of venom
> The authors' statement that "The poison of
> Sinornithosaurus may have been similar in properties to rear-fanged
> snakes and helodermid lizards in that it did not kill the envenomated
> animal quickly but rather placed it into a rapid state of shock" seems
> to be wholly unsubstantiated speculation.. The toxicity of the venom, if any, 
> is completely unknown, and no lines of evidence are brought to bear here.
>
> 2) Tooth length
> The authors write that "The anterior maxillary teeth are so long and 
> fang-like that the animal appears to be saber-toothed." yet they make no 
> effort to provide measurements of the teeth relative to tooth row length or 
> any other metric, and they provide no comparison to other taxa. They provide 
> only one measurement, the length of the largest maxillary tooth in IVPP 
> V12811, which is provided as "12mm long". This does not seem out of the range 
> of tooth proportions for tetrapods in general.
>
> Moreover, they note "Interestingly, much of the effective erupted length of 
> the teeth is
> composed of the tooth root." The type skull is also semi - disarticulated. 
> These seem to strongly suggest that the teeth have fallen out of their 
> sockets, yet this possibility is not addressed.
>
> 3) The inference of venomousness
> The authors cite Folinsbee et al. (2007) in stating "Pocketing within the 
> maxilla in conjunction with grooved fangs is considered well supported 
> evidence for
> venom delivery systems in fossil taxa" But, in fact, Folinsbee et al. suggest 
> that the hypothesis of venomousness is only "fairly well supported", in two 
> extinct species, one therocephalian with hollow, tubular, teeth, and a 
> soricine with
> strong similarities to Solenodon. They urge caution in assigning venomousness 
> to extinct species. In particular they point out that grooved teeth are 
> widely distributed in non - venomous species.
>
> 4) Maxillary pitting
> The authors describe a new feature, a "subfenestral fossa", marked by a 
> pitted area of the maxilla, ventral to the anterior antorbital fenestra. They 
> do not mention that this pitting is much more extensive, and that there may 
> be no distinction in the amount of pitting across the entire antorbital 
> fossa. Xu&Wu (2001) describe "a number of pits and ridges on the 
> anterolateral surface of the antorbital fossa" (see Fig. 4B), but they do not 
> reconstruct any distinct subfenestral fossa. Moreover, some observers believe 
> that this pitting is an artifact of preparation, where the extremely thin 
> outermost layer of bone has been damaged in
> several specimens (Mark Norell, personal communication).
>
> 5) Plucking specializations
> The authors also suggest that the premaxillary teeth functioned in plucking 
> the feathers off of Sinornithosaurus' prey, and that the maxillary teeth are 
> exceptionally long in order to penetrate the feathers. In neither case do 
> they offer examples of other animals that have specialized teeth for preying 
> on birds or processing feathers. Indeed, one might speculate that the 
> premaxillary teeth of Sinornithosaurus functioned to preen the animal's OWN 
> feathers, rather than pluck off the feathers of its prey, and one would have 
> made an equally strong inference, with exactly no support. This tendency of 
> the authors to assign functions to characters without support seems 
> particularly unscientific.
>
> Overall, the paper seems to be more an
> attempt to paint a colorful functional scenario, rather than to make a 
> rigorous scientific study of the material. It is weakened by overstatement 
> and speculation.
>
>
>
>