So can i not take claws or tail or anything like that on a shadow eidolon?

[Malik Gyan Daumantas]

I probably can't but it still seems kinda stupid specially on a form that can take a quadruped form.

[TxSam88]

Shadow
Source PPC:BOS

Base Form(s): Biped (claws, limbs [arms], limbs [legs]), quadruped (limbs [legs, 2], bite), or serpentine (bite, improved natural armor, reach [bite], tail, tail slap).

depends on the form, but yes...