Re: Thecodont questions

[Nick Longrich <longrich@phoenix.Princeton.EDU>]

Looking at modern dinosaurs, you will notice unusually rugose skulls in
species that really like to kick the *#$^% out of each other (e.g.
steamer-ducks, the Rodriguez Island Solitaire) so while obviously
Dilophosaurus wasn't doing that, I wonder if some of the rugosity in,
say, a Tyrannosaur skull relates to intraspecific agression. You can also 
see a picture of a very rugose giraffe skull in R. McNiell Alexander's
"Bones", giraffes you will recall use those ossicones on the head to
thwack each other in the sides. So I don't think claims of tyrannosaur
head-butting are necessarily as far-fetched as they might seem- although
obviously we shouldn't be overly quick to compare modern avians and
giraffes with five-tonne monstrosites whose mouths are lined with
six-inch teeth, either. 
> As far as the function of this ridge concerns, I
haven't read 
> anything about it but I'd suppose (speculation of course) it was the 
> same of the cranial ornaments in e.g. neoceratosaurs, allosaurs and 
> tyrannosaurs:
> intraspecific display.
> 
> 
> > 2) How are the forelimbs of Desmatosuchus best described (choose 
> > one):
> > 
> > -a bit longer than hindlimbs
> > -same length as hindlimbs
> > -a bit shorter than hindlimbs
> > -much shorter than hindlimbs
> 
> In Desmatosuchus haplocerus, the best known D. species, the forelimbs 
> seem to be about half as long as the hindlimbs, and quite more 
> gracile, the animal however undoubtedly being an obligate quadruped. 
> In Long and Murry's 'Carnian and Norian tetrapods from the 
> American Southwest' a figured humerus measures about 25cm, the femur 
> about 40cm. In the same volume a figured reconstruction of D. has 
> about the same limb proportions as in the well known 'Stagonolepis 
> reconstruction' which you find in every handbook. 
> However, I seem to remember Chatterjee mentioned a new, highly 
> derived Desmatosuchus species found in the Dockum near Post (Texas) 
> which he tentatively attributed a facultative bipedal posture (in 
> Padian's 'The beginning of the Age of Dinosaurs'); I haven't heard 
> anything more of this unfortunately, maybe someone else has.
> 
> Pieter Depuydt
>  
>