Parece que cabe principalmente ao GM decidir se você ainda pode conjurar ou não feitiços enquanto polimorfiado, mas alguns formulários nunca serão um problema.
A partir das Regras mágicas sobre os feitiços polimórficos:
When you cast a polymorph spell that changes you into a creature of the animal, dragon, elemental, magical beast, plant, or vermin type, all of your gear melds into your body. Items that provide constant bonuses and do not need to be activated continue to function while melded in this way (with the exception of armor and shield bonuses, which cease to function). Items that require activation cannot be used while you maintain that form. While in such a form, you cannot cast any spells that require material components (unless you have the Eschew Materials or Natural Spell feat), and can only cast spells with somatic or verbal components if the form you choose has the capability to make such movements or speak, such as a dragon. Other polymorph spells might be subject to this restriction as well, if they change you into a form that is unlike your original form (subject to GM discretion). If your new form does not cause your equipment to meld into your form, the equipment resizes to match your new size.
Uma observação importante: qualquer criatura que possa ter níveis de classe pode se tornar um conjurador, mesmo que sua forma natural esteja muito longe de ser humanóide. Isso permite que animais mágicos de várias formas desenvolvam habilidades de conjuração.