Using wild shape or beast shape, when you choose a Giant Porcupine do you get the quills ability? Its not listed within the beast shape spell, which as a specific spell over rules the more general polymorph rules.
While under the effects of a polymorph spell, you lose all extraordinary and supernatural abilities that depend on your original form (such as keen senses, scent, and darkvision), as well as any natural attacks and movement types possessed by your original form. You also lose any class features that depend upon form, but those that allow you to add features (such as sorcerers that can grow claws) still function. While most of these should be obvious, the GM is the final arbiter of what abilities depend on form and are lost when a new form is assumed. Your new form might restore a number of these abilities if they are possessed by the new form.
So the general rules seem to indicate that you get abilities and likely leaves it upto the spell, but a giant porcupine really should have quills.