This spell does not have a direct equivalent in vanilla.
Polymorph Other
Level: 5
School: Alteration
Sphere: Animal
Range: Long
Duration: Permanent
Casting Time: 5
Area of Effect: 1 creature
Saving Throw: Polymorph negates
Polymorph Other is a powerful magic that permanently alters the form of the creature affected. The target’s mental attributes are not affected and they do not receive the special abilities of the new form, but physical attributes are changed to adhere to the new form and the affected creature loses any special abilities it had in its original form. This particular version of the spell will transform the recipient into a squirrel unless a save vs. polymorph is made successfully. The effectiveness of this spell is dependent upon the target’s level, with weak creatures being relatively easy to transmute and more powerful creatures being very difficult. Creatures with less than 8 HD/levels save at a -4 penalty, those with 8 - 14 HD/levels save normally, and those with 15 or more HD/levels save with a +2 bonus. The transformation is instant and permanent until a dispel magic is cast successfully upon the affected creature.
Note that all clothes and equipment that the target was wearing will mold into the new form. However, they will return to their previous state once the target dies or the effects are dispelled.