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

Re: Crocodilian vs Avian looks



> Just to play Devils Advocate, but who says they had
> anything in them at all? Why not just small areas 
> that reduce weight and don't affect structural 
> integrity. 

I think it's very unlikely these foramina serve no
purpose, mainly because they seem to be homologous to
the foramina seen in birds and crocs - indicating
presence of some organ.

> Also, I'm not sure what corpuscles or herbsts are, 
> but, just for the sake of speculation (and perhaps 
> showing my ignorance), could these have been scent 
> glands? 

Well, both herbst and pacinian corpuscles sense
vibrations (collectively they are called
mechanoreceptors). Crocs use them to sense pressure
waves in the water created by their prey. Birds
(especially wading birds) do exactly the same thing.
Their bills are very sensitive, which is why you see
them running their beaks through the water back and
forth. These organs are not restricted to the head,
though....crocs have them over their entire body, and
some birds have them in their legs. As for the scent
gland idea, I seriously doubt it. There is the
possibility a scent gland was located in the
antorbital fossa, though, and maybe in the ventral
portion of the orbit (analogous to african antelope).
 
> In most coelophysoids (with the exception of
> _Dilophosaurus_), the subnarial gap is very small, 
> and would most likely be almost entirely obscured by
> flesh, regardless of the presence of lips.
> Why would dromaeosaurs be the exception, by the way?

Crocodilians have small alveolar gaps, and you can see
them quite well, even when covered by flesh. If the
subnarial gap was filled with skin (like the
Dilophosaurus of Jurassic Park) I would think the
animals gums would regularly be bleeding by
penetration of the enlarged dentary tooth. The reason
I suggested dromies (and probably other small
theropods) have lips or labial ridges of skin is
because bird beaks have sharp edges, so i'm assuming
that the less keratinous precursor of avian beaks
would probably have a sharp beak-shaped snout (like
those of Sinornithosaurus, Microraptor, and
Archaeopteryx). If you've ever had the chance to feel
a caiman or alligator snout, you'll see that the skin
is pretty hard, so croc-snouted theropods wouldn't
have to change much in order to achieve an avian beak.
More speculation on my part, but I think it has some
basis in reality.     

__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - Buy the things you want at great prices.
http://auctions.yahoo.com/