Re: Giant Extinct Australian Geese

[longrich@alumni.princeton.edu]

On Thursday, August 15, 2002, at 01:18 PM, Williams, Tim wrote:
> There may be some variation within the family on that score.  According 
> to
> one source, amino acid analysis of eggshells attributed to _Genyornis_
> indicates a herbivorous diet.  And dromornithid talons don't appear 
> designed
> for shredding prey.  But look at the jaws of _Bullockornis_ - could it 
> be
> anything other than a carnivore?
	Well, the herbivorous takahe has a very robust skull and mandible, 
as in Diatryma or Bullockornis, and much moreso than carnivores like 
phorusrhacids or hawks, and parrots or seed-eating finches also have 
massive beaks, so it is consistent with more than one interpretation. In 
addition, phorusrhacids, owls, and hawks have very well developed 
hooking of the upper mandible, which is absent from Diatryma and 
Bullockornis. One would predict that a specialized carnivore would show 
this.

	Now parrots are pretty interesting. I was sure that the elongate 
quadrate condyle was giving them a sliding-jaw motion of the dentary as 
in oviraptorosauria and dicynodonts... the similarity between the shape 
of the lower jaws of _Citipati_ and a macaw is just uncanny. From what I 
can tell, though, this isn't the case- the elongate quadrate condyles 
have their long axes inclined relative to each other so that sliding is 
pretty restricted and the jaw acts more like a hinge, maybe with some 
left-right rotational movement. The guys with the 
oviraptorosaurian/dicynodont-like quadrate-articular complexes are, get 
this...
	Galliformes.
	Its dangerous to overgeneralize, but generally galliformes are 
eating a large amount of plant matter, with some other stuff like 
insects, fruits, seeds etc. thrown in, although none that I know of have 
particularly elongate dentary symphyses or deep jaws like in the 
oviraptorosauria. Interesting implications for the oviraptorosauria.