Afterthought on animal symbolism

[potioncat]

 "Carol" <justcarol67 at ...> wrote:
snip:
 as well as ravens
> (which ought, IMO, to be Ravenclaw's symbol) 

Potioncat:
I used to think so too. But I read somewhere that it's raven claw, not 
raven's claw. Which makes it a black claw. Although, I thought Eagles 
had a yellow/brown claw.

For that matter, why isn't Gryffindor's animal a gryffin? And why are 
all these tokens Muggle animals rather than magical ones?